On strong n-perfect rings
  In this paper we introduce the notion of "strong $n$-perfect rings" which is in some way a generalization of the notion of "$n$-perfect rings". We are mainly concerned with those class of rings in the context of pullbacks. Also we exhibit a class of $n$-perfect rings that are not strong $n$-perfect rings. Finally, we establish the transfer of this notion to the direct product notions. 
A. Jhilal and N. Mahdou