Open Journal Systems (unknown number of records) Repositorio Español de Ciencia y Tecnología - 30 September 1993 [Record Details] |
SciELO - Cuba (unknown number of records) - 1 April 1993 [Record Details] |
Biblioteca Digital de Teses e Dissertacoes (BDTD) (unknown number of records) - 28 February 1993 [Record Details] |
Johnson Space Center (unknown number of records) - 1 January 1993 [Record Details] |