On the existence and construction of proper costratifying systems
  In this paper we further study the notion of proper costratifying systems, defined in \cite{MPV}. We give sufficient conditions for their existence, and investigate the relation between the stratifying systems defined by K. Erdmann and C. S\'aenz in \cite{ES} with the proper costratifying systems. 
Octavio Mendoza, Maria In\'es Platzeck and Melina Verdecchia
math.RT