Contragredient Lie algebras and Lie algebras associated with a standard   pentad
  We will construct standard pentads which are analogues of Cartan subalgebras, and moreover, we will study graded Lie algebras corresponding to these standard pentads. We call such pentads pentads of Cartan type and describe them by two positive integers and three matrices. The structures of their corresponding Lie algebras are related with contragredient Lie algebras. 
Nagatoshi Sasano
math.RT