中国科学院数学与系统科学研究院期刊网
PROBLEM OF EQUIVALENCE OF THE INTEGRAL ∫F(x, y, y′, y″,…, y~((n))) dx
孫本旺
Acta Mathematica Sinica, Chinese Series . 1954, (2): 223 -243 .  DOI: 10.12386/A1954sxxb0013