共 56 条
[4]
[Anonymous], 1945, MATH GAZ
[5]
Barbeau E., 1995, J DIFFER EQU APPL, V1, P291
[9]
Berg L, 2002, Z ANAL ANWEND, V21, P1061
[10]
Brand L., 1955, Amer. Math. Mon., V62, P489, DOI [10.2307/2307362, DOI 10.2307/2307362]