@inproceedings{inproceedingsaf7025a4,
title   = {On a new extension of Liapunov's direct method to discrete equations},
author = {Carvalho, Luiz Antonio Vieira De and Ferreira, Raimundo R},
year = {1987},
publisher = {SBM},
booktitle   = {Seminário Brasileiro de Análise}
}