Chapter one is divided into two parts: in the first part, we give the simple summarize of adjointness of differential operator product;
第一章：引言和预备知识部分，主要是关于微分算子的积算子自伴的研究情况和对称微分算子的一些基本知识。
2
In this paper, we get the self-adjointness of the product operators generated by different two differential expressions by operator theory and matrix calculation.
In this paper, that the formula of cannot be tenable is pointed out because of the component of the momentum functor not always satisfying the self-adjointness in the curvilinear coordinate system.