Pineda, Olga. El cuchillo de piedra; : an adventure story of Ecuador for beginning Spanish students. [electronic resource] / Edited by Odette Hofer De Scott and Willis Knapp Jones. Illus. by Jean Reinecke Held.. — New York, : Appleton-Century-Crofts, [1964]. — vi, 225 p. : illus. 21 cm.