H. El-Owaidy, A. A. S. Zagrout. ON OSCILLATIONS OF PERTURBED SECOND ORDER DIFFERENTIAL EQUATION[J]. 数学物理学报(英文版), 1983, 3(2): 121-124.
H. El-Owaidy, A. A. S. Zagrout. ON OSCILLATIONS OF PERTURBED SECOND ORDER DIFFERENTIAL EQUATION[J]. Acta mathematica scientia,Series B, 1983, 3(2): 121-124.