Paper Citation Record · LEDGER

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot

As of 6 August 2026, this Paper Citation Record lists 48 of 48 outbound references and 0 inbound Pith citation observations for arXiv:2604.22547.

A citation records a reference. It does not transfer a finding from one paper to another.

pith.paper-citation-record.v1
2604.22547 v1

Coverage vector

measured 48 of 48 reference resolution

Typed states for the displayed outbound observations.

Source: paper_references, paper_reference_links, observed 2026-05-08T10:20:21.703654Z

measured 48 of 48 standing notices

One-hop event checks from named stored sources.

Source: scholarly_work_events, retraction_status_cache, observed 2026-08-05T06:32:48.257954+00:00

measured 0 of 0 inbound itemization

Pith citing papers itemized under the disclosed page cap.

Source: paper_references, paper_reference_links

measured 0 of 1 external citation measurements

A source-named dated measurement, never combined with another source.

Source: cited_works

Reference resolution

48 of 48 outbound references displayed

verified exact40
verified fuzzy0
unresolved0
parse uncertain0
malformed identifier5
metadata mismatch3

External citation measurements

No source-named external measurement is stored.

Outbound references

Observation d14be57d-31e1-4437-8546-45a232de0087 · outbound

This paper cites Silicon quantum electronics.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Silicon quantum electronics

Reference 1

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.930047Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 87901a48-7450-493d-8838-afdf9cdf787d · outbound

This paper cites Chatterjee , author P.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Chatterjee , author P

Reference 2

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.925113Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 8e09b677-4896-4686-80f7-6877b4435ddf · outbound

This paper cites Burkard, T.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Burkard, T

Reference 3

Resolution: metadata mismatch; doi, observed 2026-05-08T22:04:18.943306Z

Source-reported events for the cited work

correction dated 2023-06-14. Source: crossref record 10.1103/revmodphys.95.025003->10.1103/revmodphys.95.025003:correction, observed 2026-07-11T02:56:26.528749+00:00. This notice travels one citation hop only.

Observation d434c044-c9eb-4cca-8da7-1d5b7f5db875 · outbound

This paper cites Steinacker, N.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Steinacker, N

Reference 4

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.950256Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation a0c9b473-1056-45ad-80bb-5de4c89fb037 · outbound

This paper cites Phys.4, 776–779, DOI: 10.1038/nphys1053 (2008).

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Phys.4, 776–779, DOI: 10.1038/nphys1053 (2008)

Reference 5

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.953372Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation b784c7e6-3723-4e00-8433-310e8431c451 · outbound

This paper cites npj Quantum Inf.9, 107, DOI: 10.1038/s41534-023-00776-8 (2023).

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot npj Quantum Inf.9, 107, DOI: 10.1038/s41534-023-00776-8 (2023)

Reference 6

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.946990Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 14ed0c65-3e8e-4015-9601-b70621c92c17 · outbound

This paper cites Industrial300mmwaferprocessedspinqubitsinnatural silicon/silicon-germanium.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Industrial300mmwaferprocessedspinqubitsinnatural silicon/silicon-germanium

Reference 7

Resolution: metadata mismatch; doi, observed 2026-05-08T22:04:18.933775Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 63582329-d22a-4d8d-aa48-91d45d901705 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 8

Resolution: malformed identifier; raw_fallback, observed 2026-05-26T15:17:35.562669Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 0ffa8b0c-1452-4018-8de2-8f36991f8646 · outbound

This paper cites J.et al.Universal logic with encoded spin qubits in silicon.Nature615, 817–822, DOI: 10.1038/ s41586-023-05777-3 (2023).

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot J.et al.Universal logic with encoded spin qubits in silicon.Nature615, 817–822, DOI: 10.1038/ s41586-023-05777-3 (2023)

Reference 9

Resolution: malformed identifier; raw_fallback, observed 2026-05-26T15:17:35.569634Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 21021dac-0411-4978-971a-0da0474a9770 · outbound

This paper cites H.et al.Spin-valley lifetimes in a silicon quantum dot with tunable valley splitting.Nat.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot H.et al.Spin-valley lifetimes in a silicon quantum dot with tunable valley splitting.Nat

Reference 10

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.742854Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 9bf11342-2380-43fb-914c-28a1d6ac2d58 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 11

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.920081Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation f0222aea-be0d-4d98-9184-238954a441e9 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 12

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.739189Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation befcaca5-7294-4774-9e3a-3734d43541ec · outbound

This paper cites M.et al.A silicon metal-oxide-semiconductor electron spin-orbit qubit.Nat.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot M.et al.A silicon metal-oxide-semiconductor electron spin-orbit qubit.Nat

Reference 13

Resolution: malformed identifier; raw_fallback, observed 2026-05-26T15:17:35.566193Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation eb349eb9-593e-4788-96f7-59c903307307 · outbound

This paper cites J., Edge, L.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot J., Edge, L

Reference 14

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.746042Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 17cf70d4-2306-4991-b43f-caf0370c27a2 · outbound

This paper cites The starting dataset is the spectral power of singlet return probability as a function of manipula- tion time for a range of applied magnetic field strengths and orientations.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot The starting dataset is the spectral power of singlet return probability as a function of manipula- tion time for a range of applied magnetic field strengths and orientations

Reference 15

Resolution: malformed identifier; arxiv_id, observed 2026-05-11T20:06:08.929729Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation c4841c29-c988-441b-936d-83eb99704098 · outbound

This paper cites Peetroons, X.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Peetroons, X

Reference 16

Resolution: verified exact; arxiv_id, observed 2026-05-11T20:06:08.933580Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 060388a2-ba67-46a9-ba9a-4edeea0d39a6 · outbound

This paper cites Elsayed , author M.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Elsayed , author M

Reference 17

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.751344Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation a6641d89-256d-4480-9f05-70886f3e2f2c · outbound

This paper cites 3-D Self-aligned Stacked NMOS-on-PMOS Nanoribbon Transistors for Continued Moore’s Law Scaling.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot 3-D Self-aligned Stacked NMOS-on-PMOS Nanoribbon Transistors for Continued Moore’s Law Scaling

Reference 18

Resolution: metadata mismatch; arxiv_id, observed 2026-05-08T22:04:18.756657Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation cf26acf8-2159-497f-a5e5-8d6f7e46f891 · outbound

This paper cites Single-shot read-out of an individual electron spin in a quantum dot.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Single-shot read-out of an individual electron spin in a quantum dot

Reference 19

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.760202Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation beae2b43-fddc-4d7a-817a-5d1137c691db · outbound

This paper cites Phys.21, 063011, DOI: 10.1088/1367-2630/ab242c (2019).

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Phys.21, 063011, DOI: 10.1088/1367-2630/ab242c (2019)

Reference 20

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.888273Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 17eaf6ab-8748-465d-ac53-32e10dec8093 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 21

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.913329Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation d22e1a05-e3f3-4a1c-a088-51ea00192440 · outbound

This paper cites D.et al.Bounds to electron spin qubit variability for scalable cmos architectures.Nat.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot D.et al.Bounds to electron spin qubit variability for scalable cmos architectures.Nat

Reference 22

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.767246Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 275219f1-f733-4d51-b97b-76b799ceff8a · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 23

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.879109Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 0bb3b8ac-4353-40c7-9f57-2417c84f0efc · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 24

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.882389Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 5c7e16e6-702c-4aea-b1f1-7401eb0009e6 · outbound

This paper cites & Széchenyi, G.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot & Széchenyi, G

Reference 25

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.810481Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 6e41e15e-3735-4422-95f8-c538bdadf408 · outbound

This paper cites Physical Review Letters 85(10), 2200–2203 (2000).

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Physical Review Letters 85(10), 2200–2203 (2000)

Reference 26

Resolution: malformed identifier; doi, observed 2026-05-08T22:04:18.796196Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 5f1fe156-ed6b-47dd-9aae-c0f17b7d0316 · outbound

This paper cites & Niquet, Y .-M.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot & Niquet, Y .-M

Reference 27

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.867566Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 63d76773-0712-4d40-acb4-c2dacba88528 · outbound

This paper cites Adv.8, eabq0455, DOI: 10.1126/sciadv.abq0455 (2022).

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Adv.8, eabq0455, DOI: 10.1126/sciadv.abq0455 (2022)

Reference 28

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.790582Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 3cc6d72d-18ff-4a1e-8b46-543092c4cf60 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 29

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.786394Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation bc973653-f2d3-4095-b391-dc1e07175517 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 30

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.864405Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation f1d46fe0-ea21-4e4c-b6bf-e288c1952bb1 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 31

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.872661Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 1b611367-0bfa-4142-8439-abade6ca6f86 · outbound

This paper cites Ferdous , author K.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Ferdous , author K

Reference 32

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.891707Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 75c2b1ca-4732-4df7-b26e-6725e16ccbb3 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 33

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.907053Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation ec25c3ec-4c0e-410e-89ef-7e789933d0a3 · outbound

This paper cites F.et al.Radio-frequency cascade readout of coupled spin qubits fabricated using a 300~mm wafer process (2025).

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot F.et al.Radio-frequency cascade readout of coupled spin qubits fabricated using a 300~mm wafer process (2025)

Reference 34

Resolution: verified exact; arxiv_id, observed 2026-05-11T20:06:08.937555Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 1de3c60c-66ed-4cdd-88c7-f8b33114c599 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 35

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.855103Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 12401d93-f25f-4b6d-92cd-6f2ca31de48b · outbound

This paper cites Critical-Field Study of Superconducting Aluminum.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Critical-Field Study of Superconducting Aluminum

Reference 36

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.838183Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 90518a0d-b6c9-47ec-b1d9-c44e81f096d3 · outbound

This paper cites Thickness and temperature dependence of the critical magnetic field of thin superconducting films of the aluminium group metals.Acta Phys.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Thickness and temperature dependence of the critical magnetic field of thin superconducting films of the aluminium group metals.Acta Phys

Reference 37

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.833339Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 6d00b806-6470-4b31-a17c-178c5c07130d · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 38

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.806349Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation d480eb5e-b4ea-4173-ab66-9fd412ad145c · outbound

This paper cites J.et al.Electric-field tuning of the valley splitting in silicon corner dots.Appl.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot J.et al.Electric-field tuning of the valley splitting in silicon corner dots.Appl

Reference 39

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.848271Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation cec84326-2819-4020-8fef-631e287023d2 · outbound

This paper cites K.et al.Valley splitting of single-electron si mos quantum dots.Appl.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot K.et al.Valley splitting of single-electron si mos quantum dots.Appl

Reference 40

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.842203Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 38c3af6a-9043-4020-950c-a42ff4cd6bf0 · outbound

This paper cites Phys.3, 41–45, DOI: 10.1038/nphys475 (2007).

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Phys.3, 41–45, DOI: 10.1038/nphys475 (2007)

Reference 41

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.818324Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation a1d79a5f-9579-48dc-81f3-52031055d05b · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 42

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.825786Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation f17c726e-37f1-4362-b18d-5d68023a9cc6 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 43

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.814510Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 4501f27d-6191-4ffe-9786-6e26cd712335 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 44

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.821782Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 7fe9c0f0-727c-4e3b-81f1-b0897dfdbbfc · outbound

This paper cites Universal control of a six-qubit quantum processor in silicon.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Universal control of a six-qubit quantum processor in silicon

Reference 45

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.861090Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 5e4f2a6f-143c-418d-bf20-0c098245e512 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 46

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.903371Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation 37f46ee7-a6d8-4b8b-b6c3-cce96606cfa1 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 47

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.922531Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Observation d87e8e5d-985a-46dd-8bf8-43f01473a8e7 · outbound

This paper cites an unresolved cited work.

Valley enhanced Rabi frequency in n-type planar Silicon-MOS quantum dot Unresolved cited work

Reference 48

Resolution: verified exact; doi, observed 2026-05-08T22:04:18.896173Z

Source-reported events for the cited work

No event found in the named queried sources as of 2026-08-05T06:32:48.257954+00:00.

Pith citing papers

No inbound Pith citation observations are available.