摘要
Let i and e be two elements generating Douglis algebra （Commu. on Pure and Appl. Math., 6（1953）, 259）, they are subject to the multiplication rules i2=-1, ie=ei, er+1=0, e0=1 （r is a positive integer）. In wide applications to plane elastic theory some elliptic systems can be written as simple form Dw+Aw+B（?）=F, where D
