Published in Boletin Soc Biol Concepcion, in 1975, in volume 49, pages 61-70

Published in Boletin de la Sociedad de Biología de Concepción, in 1975, in volume 49, pages 71-77

Published in Boletin Soc Biol Concepcion, in 1975, in volume 49, pages 177-184