摘要
In [1—3], we have discussed problems on the Putnam-Fuglede theorem of non-normal operators which reduce AX=XB’（AXB=X） to A*X =XB* （A*XB* =X）. For the normal operators the following problems are considered: Let （N1, …,Nn） and （M1,…, Mn） be two groups of commuting normal operators, and we
