Two pairs of congruent point range and pencils are found between two projective planesof the same element.
同素对应的两射影平面场存在两对对应合同点列，两对对应合同线束。
In this paper, we mainly discuss the relations and the properties of Wn-modules and dual exact sequences, and give some applications on the finitely presented modules over coherent rings.
本文讨论了Wn-模与对偶正合列的性质和关系,且给出了它们在讨论凝聚环上的有限表现模时的一些应用。