APA

National Council of Teachers of Mathematics, . (1971). Geometria informal. México: Trillas.

Chicago

National Council of Teachers of Mathematics, . 1971. Geometria informal. México: Trillas.

Harvard

National Council of Teachers of Mathematics, . (1971). Geometria informal. México: Trillas.

MLA

National Council of Teachers of Mathematics, . Geometria informal. México: Trillas. 1971.