L. Wang
College of Mathematics and Statistics, Northwest Normal University, Lanzhou 730070, Gansu, P. R. China.
[ 1 ] - Every class of $S$-acts having a flatness property is closed under directed colimits
Let $S$ be a monoid. In this paper, we prove every class of $S$-acts having a flatness property is closed underdirected colimits, it extends some known results. Furthermore thisresult implies that every $S$-act has a flatness cover if and only if it has a flatness precover.