The numerical solution of large finite element systems by explicit preconditioning semi-direct methods Elias A. Lipitakis; George A. Gravvanis — 1991 Δελτίο της Ελληνικής Μαθηματικής Εταιρίας
The Convergence rate and Complexity of Precondotioned Iterative methods based on Approximate finite Element matrix Factorization Elias A. Lipitakis; George A. Gravvanis — 1992 Δελτίο της Ελληνικής Μαθηματικής Εταιρίας