Pith. sign in

REVIEW 3 major objections 6 minor 39 references

Operational vs. Umbral Methods and Borel Transform

T0 review · 3 major / 6 minor · reviewed 2026-08-14 · deepseek-v4-flash

Pith's one-line read The paper claims that Borel-type integral transforms unify umbral and operational methods, so that integrals and generating functions of special functions reduce to formal algebraic manipulations.

desk verdict A useful formal toolkit for special-function integrals, but the central permanence principle is unsafe as stated and Example 18 gets a factor √π wrong. read the letter →

arxiv 1908.04160 v1 pith:GE6MT6WI submitted 2019-08-12 math.CA

classification math.CA MSC 05A4044A9947B9947A6233C5233C6533C9933B10
keywords umbralcalculusBoreltransformoperationalmethodsspecialfunctionsgeneratingHermitepolynomialsLaguerreBessel
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper argues that Borel-type integral transforms, read as operators $\Gamma(\alpha x \partial_x + 1)$, supply the link between umbral calculus and operational differintegral methods. Its central claim is that once a special function is given an umbral image—Bessel functions become Gaussians, Tricomi functions become exponentials—the umbral operator can be treated as an ordinary constant, and integrals, derivatives, and generating functions follow from elementary algebra. That matters because it offers one template for deriving integrals of special functions and lacunary generating functions that previously required bespoke analytic or combinatorial arguments. The authors present the method as a computational principle and explicitly allow formal manipulation of divergent series, so the permanence of formal properties functions as the load-bearing premise.

What carries the argument

The load-bearing machinery is the pair consisting of the umbral vacuum $\phi_\nu = 1/\Gamma(\nu+1)$ with the shift operator $\hat c = e^{\partial_z}$, and the Borel-type operator $\hat B_\alpha = \Gamma(\alpha x\partial_x+1) = \int_0^\infty e^{-t} t^{\alpha x\partial_x}\,dt$. The vacuum converts special functions into binomial and exponential expressions—$J_0(x) = e^{-\hat c (x/2)^2}\phi_0$, $H_n(x,y) = (x+y\hat h)^n\theta_0$—while the Borel operator and its inverse move between the special function and its simpler image. The argument is carried by the "principle of permanence of formal properties" (Theorems 2 and 4): once an umbral correspondence is set, the operator may be handled as a constant in integrals, derivatives, and series sums, with Gamma-function algebra doing the computational work.

What would settle it

Compute both sides of eq. (57) numerically for a non-Gaussian integrable function, say $f(x)=e^{-|x|}$ with $\alpha=1/2$: the theorem predicts $\int_{-\infty}^{\infty}\hat B_{1/2}[f](x)\,dx = 2\Gamma(1/2)$, so direct quadrature of the double integral either confirms the interchange or reveals where the formal rule breaks. Alternatively, evaluate the inverse relation (54) at $x=1$ through the Hankel contour of eq. (56) and compare with $J_0(1)$.

Watch

Extended reading notes

Core claim

The central discovery is that the fractional Borel operator $\hat B_\alpha = \Gamma(\alpha x \partial_x + 1)$, together with its inverse, connects the umbral representation of special functions to ordinary exponential and Gaussian algebra. In this formalism $J_0(x)=e^{-\hat c (x/2)^2}\phi_0$, $C_0(x)=e^{-\hat c x}\phi_0$, and $H_n(x,y)=(x+y\hat h)^n\theta_0$; Theorem 4 states that the $\alpha$-order Borel anti-transform of $f(x)=\sum_r f_r x^r$ is $\sum_r f_r(\hat c \alpha x)^r \phi_0$, with $\hat c$ treated as an ordinary constant under integration, differentiation, and summation. The authors use this to obtain $\int_0^\infty J_0(x)\,dx = 1$, $\int_0^\infty J_0(x) x^{\nu-1}\,dx = 2^{\nu-1}\Gamma(\nu/2)\Gamma(1-\nu/2)$, the Doetsch rule and its lacunary extensions, and generating functions for Laguerre, associated Hermite, higher-order Hermite, and generalized heat polynomials.

Load-bearing premise

The claim rests on the principle of permanence of formal properties: once an umbral correspondence is established, the umbral operator may be treated as an ordinary constant under derivatives, integrals, and series summation, even when the resulting series diverge.

Editorial extensions

If this is right

  • Bessel-function integrals reduce to Gaussian integrals and Gamma functions; for example $\int_0^\infty J_0(x)\,dx = 1$ and $\int_0^\infty J_0(x)x^{\nu-1}\,dx = 2^{\nu-1}\Gamma(\nu/2)\Gamma(1-\nu/2)$ for $0<\nu<3/2$.
  • The half-order Borel transform interchanges $J_0(x)$ and $e^{-(x/2)^2}$, so Bessel integrals can be evaluated through Gaussian integration and the inverse transform, as in eqs. (52)–(59).
  • Lacunary generating functions for Hermite polynomials follow by exponentiating the binomial form $H_n(x,y)=(x+y\hat h)^n\theta_0$; this yields the Doetsch rule and the triple lacunary Hermite generating function via third-order Hermite polynomials.
  • Borel–Leroy and B-Borel generalizations turn exponentials into Bessel-Wright and Mittag-Leffler functions and produce integral evaluations such as $\int_{-\infty}^{\infty} E_{(1,\beta+1)}(-x^2)\,dx = \pi/\Gamma(\beta+1/2)$.
  • The umbral Kronecker operator yields a closed formula for the $m$-th derivative of a trinomial power, Theorem 6.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If the permanence principle holds broadly, the method could be implemented as a symbolic calculus: formal power series identities would follow from binomial expansion and Gamma-function evaluation, with Borel summation supplying convergence after the fact.
  • The same bridge likely extends to multi-index families such as Wright and generalized Mittag-Leffler functions, generating new lacunary generating functions; this is a natural testable extension the paper only hints at.
  • The divergent-series cases the authors allow (eq. 50) suggest that a rigorous version of the method needs a Borel-summability hypothesis; classifying which functions satisfy it would turn the heuristic into a theorem.
Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 6 minor

Summary. The paper proposes a unification of umbral calculus and operational (differintegral) methods through Borel-type integral transforms. It introduces umbral operators such as ĉ and ĥ, together with a 'principle of permanence of formal properties' (Theorems 2 and 4), which allows the umbral operator to be treated as an ordinary constant under differentiation, integration, and series summation. Using this principle, the authors derive a large catalog of integral identities, generating functions, and series summations for special functions including Bessel, Tricomi, Laguerre, Hermite, and generalized heat polynomials. The central claim is that the merged formalism provides a new and efficient method for obtaining integrals of special functions and associated generating functions.

Significance. If the method were sound, it would offer a unifying symbolic framework for a wide class of special-function identities, and the paper contains many formulas that are plausible or correct in simple cases (e.g., the Borel transform C0(x) to e^{-x}). The generalization to α-order Borel transforms and the use of Hankel contours for the inverse are also attractive ideas. However, the reliability of the method is not established: the permanence principle is unproved and as stated overreaches, and the paper's own Example 18 yields a numerically incorrect result. The paper is best viewed as a formal calculation catalog, but the central methodological claim requires substantial justification or restriction before the results can be accepted.

major comments (3)
  1. [Section 2, Theorem 2; Section 4, Theorem 4, Eq. (61)] The 'principle of permanence of formal properties' is stated without proof and without a domain of validity. It asserts that once an umbral correspondence is established, the umbral operator can be treated as an ordinary constant under integration, differentiation, and series summation. This is not true in general without restrictive hypotheses. The authors themselves acknowledge the issue in Section 3 after Eq. (50), where interchanging the Borel operator with series summation produces a divergent series, and they explicitly say they will 'take some freedom' with such manipulations. No summability, uniform-convergence, or analytic-continuation conditions are supplied. Because Theorem 4 is used in most of the subsequent derivations, the method's reliability depends on this unproved principle; it should either be proved for the specific function classes considered or be replaced by a carefully delimited rule with precise hypotheses.
  2. [Section 7, Example 18, Eqs. (123)-(128)] The claimed closed form for I(x,y) = ∫_{-∞}^{∞} e^{-x z^2 - y z^4} dz is numerically incorrect. For x=0, y=1, the direct evaluation gives I(0,1) = ∫_{-∞}^{∞} e^{-z^4} dz = 2Γ(5/4) ≈ 1.8128. Equation (128) gives π(2)^{-1/4} D_{-1/2}(0) ≈ 3.213. Thus the coefficient π in Eq. (128) is wrong; the correct coefficient is √π (or an equivalent expression). Since this example is presented as 'a significant result' demonstrating the flexibility and reliability of the formalism, this error directly contradicts the paper's central claim. The derivation needs an independent analytic justification at least for this family of integrals, and the same caution presumably applies to other formulas obtained by the same unregulated use of the permanence principle.
  3. [Various: Eqs. (12)-(14), (29)-(30), (43)-(44), (88)] Many identities are asserted without proof or adequate reference. The derivations are often omitted or reduced to 'we find', so the reader cannot determine which results follow from the proposed method and which are simply stated ad hoc. If the paper's contribution is a method, the reader should be able to trace how the method produces these identities. The authors should either provide complete derivations (at least in outline) or explicitly label such identities as formal results requiring separate analytic verification. Otherwise the claimed efficiency of the method is weakened, since every identity would need a case-by-case check.
minor comments (6)
  1. [Abstract and Section 1] The term 'differintegral methods' is used without a definition; please define it or provide a standard reference.
  2. [Example 2, Eq. (14)] The expression (−1)^{(n−2)/4} in the second formula is ambiguous for general n; it should be written with explicit floor functions or case distinctions, since the exponent is not an integer for all n.
  3. [Section 3, Theorem 3 proof] The proof interchanges the orders of integration without stating a Fubini-type justification; please add assumptions such as absolute integrability of f(tα x) in x for each t>0.
  4. [Throughout] There are several typographical errors, e.g., 'Kampé dé Fériét' should be 'Kampé de Fériet', 'polinomials' should be 'polynomials', 'espressed' should be 'expressed', and 'follwing' should be 'following'.
  5. [References] Reference [4] is listed as 'in press' and reference [8] is a PhD thesis; please provide published versions or more complete bibliographic details where available.
  6. [Section 5, Definition 5, Eq. (89)] The notation y ĥ^r θ0 := θ_r is confusing because the subscript r is used both as a power and as an index; consider a clearer notation such as θ^{(r)}.

Circularity Check

2 steps flagged · score 4.0 of 10

The Bessel-Gaussian link is definitional and the governing permanence principle is carried by self-citations, though most displayed identities remain independently checkable.

  1. self definitional [Section 4, Proposition 5, immediately after Eq. (60)]
    "The previous statement is essentially a rewording of the Umbral definition of the Bessel functions discussed in Sec. 2."

    In Proposition 2, the umbral operator is introduced via ĉ^ν φ0 = 1/Γ(ν+1), so the expansion of e^{-ĉ(x/2)^2}φ0 coincides term-by-term with the series for J0(x). Proposition 5 then 'derives' the Bessel-Gaussian link by expanding the inverse Borel transform and re-inserting the same factorial denominators through ĉ^r φ0 = 1/r!. The paper itself concedes that this is 'essentially a rewording' of the definition. Therefore this central connection is not an independently obtained result; it is the umbral definition restated in Borel-transform language.

  2. self citation load bearing [Section 2, Theorem 2; Section 4, Theorem 4, Eq. (61)]
    "and for all the operations of integration, derivative, series summation and so on, the operator ĉ can be treated as an ordinary constant."

    This theorem is the formal license that lets the paper replace Bessel functions by Gaussian expressions, evaluate Gaussian integrals, and then re-insert the umbral operator as an ordinary constant. It is stated without proof in the present paper, and the Bessel-Gaussian correspondence on which it relies is introduced by citing the authors' own prior work (refs. [5,6,7,8], including the second author's thesis [8]). The paper even acknowledges in Section 3, after Eq. (50), that it is taking 'freedom' with divergent series. The same principle is used in Example 18 to produce Eq. (128) with an incorrect coefficient: at x=0, y=1 the paper's formula gives about 3.21, while direct evaluation of ∫ e^{-z^4} dz = Γ(1/4)/2 ≈ 1.81 requires the coefficient √π rather than π.

full rationale

The paper does not fit parameters to data, and many of its displayed identities—Doetsch-type Hermite generating functions, Laguerre generating functions, and various Bessel integral evaluations—are independently checkable special-function formulas; for those, the umbral formalism acts as compact notation rather than circular inference. The circularity concerns are localized but real. First, the Bessel-Gaussian identification is introduced by definition in Proposition 2 and explicitly acknowledged in Proposition 5 as 'essentially a rewording' of that definition, so the flagship link between Bessel functions and Gaussians is not derived from independent premises. Second, the decisive 'principle of permanence of formal properties' (Theorem 2 and Theorem 4) that converts Gaussian manipulations into Bessel identities is not proved here and is supported by the authors' own prior papers; this is load-bearing self-citation. The risk is concrete: Example 18 applies that same principle to obtain Eq. (128) with coefficient π, whereas direct evaluation gives the correct coefficient √π, showing the permanence rule as stated can produce false integral formulas. Because the paper contains many results that can be checked independently and the umbral representation is a definitional restyling rather than a fit, the overall circularity is partial rather than total.

Assumptions & free parameters 0 free parameters · 4 assumptions · 4 invented entities

The central claim rests on a formal umbral calculus whose operators are defined to match the coefficients of the target functions, on a principle of permanence that allows integrals and derivatives to commute with umbral substitutions, and on Borel operator manipulations with divergent series. There are no fitted numerical parameters. The main risk is not parameter fitting but missing convergence conditions and a reliance on the authors' own previously published formalism.

assumptions (4)
  • domain assumption Fractional negative-derivative Leibniz rule used as an identity for C∞ functions; Eq. (3) in Section 1.
    The paper applies a series form of integration by parts to C∞ functions and assumes the infinite sum converges and equals the primitive.
  • ad hoc to paper Principle of permanence of formal properties; Theorem 2 and Theorem 4 in Sections 2 and 4.
    The paper extends an umbral correspondence to integrals, derivatives, and series summation without proof of convergence or analytic continuation.
  • ad hoc to paper Formal manipulation of divergent series and formal inverses of Borel operators; Section 3 after Eq. (50) and Eqs. (53)-(56).
    The authors state they will take some freedom and include divergent series, so derived formulas are formal except where independently checkable.
  • ad hoc to paper Umbral vacuum and shift operator behave like ordinary constants under integration; Definitions 2-3 and Theorem 4.
    The method hinges on treating ĉ as a constant in integrals and then applying its defining action 1/Γ(r+1).
invented entities (4)
  • Umbral operator ĉ with vacuum φ0
    purpose: Represents factorial denominators as ĉ^r φ0 = 1/Γ(r+1), turning Bessel and Tricomi series into exponentials.
    Formal symbol used throughout; no external falsifiable handle beyond the paper's own series manipulations.
  • Hermite umbral operator y ĥ with vacuum θ0
    purpose: Writes H_n(x,y) as (x + y ĥ)^n θ0.
    Defined to match Hermite series coefficients; no independent evidence.
  • Generalized heat polynomial operator x² d̂_ν + 4y with vacuum η0
    purpose: Encodes P_{n,ν}(x,y) as a binomial power.
    Formal construction tailored to the target polynomials.
  • Umbral operator p̂_m with vacuum π0
    purpose: Used in Theorem 6 to encode x^m as e^{p̂_m x}π0.
    Formal device for the trinomial derivative formula.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Operational vs. Umbral Methods and Borel Transform." pith.science (2026). https://pith.science/paper/GE6MT6WI

@misc{pith2026190804160,
  author       = {Pith},
  title        = {Pith review of: Operational vs. Umbral Methods and Borel Transform},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/GE6MT6WI}},
  note         = {Machine review of arXiv:1908.04160}
}
read the original abstract

Differintegral methods, currently exploited in calculus, provide a fairly unexhausted source of tools to be applied to a wide class of problems involving the theory of special functions and not only. The use of integral transforms of Borel type and the associated formalism will be shown to be an effective means, allowing a link between umbral and operational methods. We merge these two points of view to get a new and efficient method to obtain integrals of special functions and the summation of the associated generating functions as well.

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

39 extracted references · 36 canonical work pages

  1. [15]

    Operational versus umbral methods and the Borel transform

    Dattoli G, Di Palma E, Sabia E, et al. Operational versus umbral methods and the Borel transform. Int J Appl Comput Mat h. 2017; 1–22

  2. [8]

    PhD Thesis: Umbral Calculus, a Di fferent Mathematical Language

    Licciardi S. PhD Thesis: Umbral Calculus, a Di fferent Mathematical Language. Mathematics and Computer Sci ences, Dep. of Mathematics and Computer Sciences, XXIX cycle, University of Catania, 2 018; arXiv:1803.03108 [math.CA]

  3. [1]

    The Fractional Calculus: Theory an d Applications of Di fferentiation and Integration to Arbitrary Order

    Oldham KB, Spanier J. The Fractional Calculus: Theory an d Applications of Di fferentiation and Integration to Arbitrary Order. Mathemati cs in Science and Engineering. 1974; 111

  4. [2]

    Appl Math and Comp

    Dattoli G, Germano B, Martinelli MR, et al.Negative deri vatives and special functions. Appl Math and Comp. 2010; 217 : 3924–3928

  5. [3]

    Fonctions Hypergeometriques and Hyperspheriques

    App´ el P , Kamp´ e de F´ eri´ et J. Fonctions Hypergeometriques and Hyperspheriques. Polynomes d’Hermite. 1926; Gaut hiers-Villars. Paris

  6. [4]

    Mathematical Me thods for Physics

    Babusci D, Dattoli G, Licciardi S, et al. Mathematical Me thods for Physics. Invited Monograph by World Scientific, 20 19. Singapore, in press

  7. [5]

    On Ramanujan Master Theorem

    Babusci D, Dattoli G. On Ramanujan Master Theorem. arXiv :1103.3947 [math-ph]

  8. [6]

    Heisenberg algebra, umb ral calculus and orthogonal polynomials

    Dattoli G, Levi D, Winternitz P . Heisenberg algebra, umb ral calculus and orthogonal polynomials. J Math Phys. 2008; 49:053–509

Show all 39 references
  1. [7]

    Symbolic methods fo r the evaluation of sum rules of Bessel functions

    Babusci D, Dattoli G, Gorska K, et al. Symbolic methods fo r the evaluation of sum rules of Bessel functions. J Math Phys . 2013; 54:073501

  2. [9]

    The Umbral Calculus

    Roman S. The Umbral Calculus. Dover Publications. 2005. New Y ork

  3. [10]

    Ramanujan’s Notebooks

    Berndt BC. Ramanujan’s Notebooks. Springer-V erlag. 1 985. New Y ork

  4. [11]

    The spherical Bess el and Struve functions and operational methods

    Babusci D, Dattoli G, Gorska K, et al. The spherical Bess el and Struve functions and operational methods. Appl Math a nd Comp. 2014; 238:1–6

  5. [12]

    On evaluation of integrals involv ing Bessel functions

    Babusci D, Dattoli G. On evaluation of integrals involv ing Bessel functions. arXiv:1111.0881 [math.CA], 2011

  6. [13]

    Integral transforms and operationalcalculus

    Ditkin V A, Prudnikov AP . Integral transforms and operationalcalculus. (trans., D.E. Brown, ed. I.N. Sneddon). 19 65. Oxford, Pergamon

  7. [14]

    Generalized polynomials, operational iden tities and their applications

    Dattoli G. Generalized polynomials, operational iden tities and their applications. J Comp and Appl Math. Elsevie r. 2000;118(12):111–123

  8. [16]

    The Euler Legacy to Modern Physi cs

    Dattoli G, Del Franco M. The Euler Legacy to Modern Physi cs. Lecture Notes of Seminario Interdisciplinare di Matema tica. 2010; 9:1–24

  9. [17]

    Critical Properties of φ4 Theories

    Kleinert H, Schulte-Frohlinde V . Critical Properties of φ4 Theories. World Scientific. 2001; 512, doi.org /10.1142/4733

  10. [18]

    Zeta Regularizations with Applica tions

    Elizalde E, Romeo A. Zeta Regularizations with Applica tions. World Scientific. 1994

  11. [19]

    Le cons sur les S´ eries Divergentes, Gauthier- Villars

    Borel E. Le cons sur les S´ eries Divergentes, Gauthier- Villars. 1928. Paris

  12. [20]

    Divergent Series, Clarendon Press

    Hardy GH. Divergent Series, Clarendon Press. 1949. Oxf ord

  13. [21]

    A note on truncated p olynomials

    Dattoli G, Cesarano C, Sacchetti D. A note on truncated p olynomials. Appl Math and Comput. 2003; 134:595–605

  14. [22]

    Lacunary Generati ng Functions for the Laguerre Polynomials

    Babusci D, Dattoli G, Gorska K, et al. Lacunary Generati ng Functions for the Laguerre Polynomials. S` eminaire Loth aringien de Combina- toire. 2017; Article B76b, 19

  15. [23]

    Summation of divergent series: Order-d ependent mapping

    Zinn-Justin J. Summation of divergent series: Order-d ependent mapping. Appl Numer Math. 2010; 60(12):1454–1464

  16. [24]

    Special Functions For Engeneers and Applie d mathematicians

    Andrews LC. Special Functions For Engeneers and Applie d mathematicians. Mc Millan. 1985. New Y ork

  17. [25]

    Une g´ en´ eralisation de l’int´ egrale de Laplace-Abel

    Mittag-Le ffler MG. Une g´ en´ eralisation de l’int´ egrale de Laplace-Abel. Comptes Rendus Hebdomadaires des S´ eances de l’Acad´ emi e des Sciences. 1903; 136:537–539

  18. [26]

    A triple lacunary generating func tion for Hermite polynomials

    Gessel I, Jayawant P . A triple lacunary generating func tion for Hermite polynomials. Electr J Combinat. 2005; 12

  19. [27]

    The heat equation

    Widder DV . The heat equation. Academic Press. 1976

  20. [28]

    Applications of the classical umbral calculu s

    Gessel I. Applications of the classical umbral calculu s. 2003; 49(4):397–434

  21. [29]

    Motzkin numbe rs: an operational point of view

    Artioli M, Dattoli G., Licciardi S, et al. Motzkin numbe rs: an operational point of view. J Integ Sequenc. 2018; 21, A rticle 18.7.5

  22. [30]

    On an umbral tre atment of Gegenbauer, Legendre and Jacobi polynomials

    Dattoli G, Germano B, Licciardi S, et al. On an umbral tre atment of Gegenbauer, Legendre and Jacobi polynomials. Int ernational Mathemat- ical Forum. 2017; 12(11):531–551

  23. [31]

    The higher-order heat-type equations via signed L´ evy stable and generalize d Airy functions

    Gorska K, Horzela A., Penson KA, et al. The higher-order heat-type equations via signed L´ evy stable and generalize d Airy functions. J Physics A: Math and Theor. 2013; 46:42

  24. [32]

    Recherches sur les polynomes d’Hermite

    Nielsen N. Recherches sur les polynomes d’Hermite. Mat hematisk-Fysiske Meddelelser. 1918; 1:79, Det. Kgl, Dansk e Videnskabernes Selskab. 21

  25. [33]

    Hermite Calcul us

    Dattoli G, Germano B, Licciardi S, et al. Hermite Calcul us. Modeling in Mathematics, Atlantis Transactions in Geom etry. 2017; 2:43–52, J. Gielis, P . Ricci, I. Tavkhelidze (eds), Atlantis Press, Paris, Springer

  26. [34]

    Theory of Communication, Part 1

    Gabor D. Theory of Communication, Part 1. J Inst of Elect Eng Part III. Radio and Communication. 1946; 93: pages 429

  27. [35]

    The History of Blissard’s Symbolic Method, wit h a Sketch of its Inventor’s Life

    Bell ET. The History of Blissard’s Symbolic Method, wit h a Sketch of its Inventor’s Life. Amer Math Monthly. 1938; 45 :7:414–421

  28. [36]

    On generalized heat polynomials

    Nasim C. On generalized heat polynomials. Int J Math and Mathemat Sciences. 1988; 11(2):393–400

  29. [37]

    Expansions in terms of heat po lynomials and associated functions

    Rosenbloom PC, Widder DV . Expansions in terms of heat po lynomials and associated functions. Trans of the Amer Math S oc. 1959; 92(2):220–266

  30. [38]

    Funzioni Speciali

    Tricomi FG. Funzioni Speciali. 1959; 408. Gheroni

  31. [39]

    Theory of General ized Trigonometric functions: From Laguerre to Airy forms

    Dattoli G, Licciardi S, Pidatella RM. Theory of General ized Trigonometric functions: From Laguerre to Airy forms. J Mathemat Anal and Appl. 2018; 468(1):103–115. 22

Pith tools

Reviewed August 14, 2026 · model on record in the stance chip above.