Some questions in the theory of one-dimensional linear differential operators of the second order. II
Keyword(s):
1990 ◽
Vol 112
(3)
◽
pp. 177-180
Keyword(s):
1957 ◽
Vol 6
(2)
◽
pp. 247-285
◽
1975 ◽
Vol 15
(3)
◽
pp. 86-94