中国科学院数学与系统科学研究院期刊网
FIXED POINT INDEX OF SET-VALUED MAPPINGS AND MULTIPLICITY OF SOLUTIONS OF ELLIPTIC EQUATIONS WITH DISCONTINUOUS NONLINEARITIES
张恭庆;姜伯驹
Acta Mathematica Sinica, Chinese Series . 1978, (1): 26 -43 .  DOI: 10.12386/A1978sxxb0003