PALAVRAS-CHAVE VOLTAR PALAVRA-CHAVE: Hylleraas’ method   Calculation of electronic energies levels of molecular ions from the Hamilton-Jacobi equation: HeH2plus, LiH3plus and BeH4plus Deise Tamara dos Santos Cavalcante Machado; Antonio Luciano A. Fonseca; Daniel L. Nascimento; Jonathas A. Campos; Antonio O. Cleves Nunes.