  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.
