共 14 条
[7]
FOSTER AL, 1964, MATH Z, V85, P169
[8]
FOSTER AL, 1964, MATH Z, V83, P147
[9]
JONSSON B, 1967, MATH SCAND, V21, P110
[10]
Pixley A. F., 1963, P AM MATH SOC, V14, P105, DOI 10.2307/2033968