Superfluids in rotation: Landau-Lifshitz vortex sheets vs Onsager-Feynman vortices

The paper by Landau and Lifshitz on vortex sheets in rotating superfluid appeared in 1955 almost at the same time when Feynman published his paper on quantized vortices in superfluid 4He. For a long time this paper has been considered as an error. But 40 years later the vortex sheets have been detected in chiral superfluid 3He-A in the rotating cryostat constructed in the Olli Lounasmaa Low Temperature Laboratory (Otaniemi, Finland). The equation derived by Landau and Lifshits for the distance between the vortex sheets as a function of the angular velocity of rotation has been experimentally confirmed, which is the triumph of the theory. We discuss different configurations of the vortex sheets observed and to be observed in superfluid 3He-A.