Identification of the minimal conserved structure of the HIV reverse transcriptase under the presence and absence of drug pressure by Ceccherini-Silberstein, F, Santoro, M, Svicher, V, Forbici, F, Gori, C, Esnouf, R, Ciccozzi, M, Alvarez, MR, D'Arrigo, R, Bellocchi, M, Balotta, C, Bertoli, A, Giannella, S, Cenci, A, Trotta, M, Balzarini, J, Monforte, A, Antinori, A, Perno, C