Echevarria, m. O. (1974). The relations of knowledge of the principles basic to the solution of a problem intelligence, and intrest, in the subject matter to the ability to solve problems [microform]. Photoduplication Service, University of the Philippines Library.

Echevarria, maximo O. The Relations of Knowledge of the Principles Basic to the Solution of a Problem Intelligence, and Intrest, in the Subject Matter to the Ability to Solve Problems [microform]. Quezon City: Photoduplication Service, University of the Philippines Library, 1974.

Echevarria, maximo O. The Relations of Knowledge of the Principles Basic to the Solution of a Problem Intelligence, and Intrest, in the Subject Matter to the Ability to Solve Problems [microform]. Photoduplication Service, University of the Philippines Library, 1974.