黄烈德. THE MODIFIED HELMHOLTZ EQUATIONS AND THEIR BOUNDARY VALUE PROBLEMS[J]. 数学物理学报(英文版), 1988, 8(2): 165-179.
Huang Liede. THE MODIFIED HELMHOLTZ EQUATIONS AND THEIR BOUNDARY VALUE PROBLEMS[J]. Acta mathematica scientia,Series B, 1988, 8(2): 165-179.