Helick, R. M. (1973). Elements of preschool playyards. Regent Graphic Services.
Citación estilo ChicagoHelick, R. Martin. Elements of Preschool Playyards. Pittsburgh: Regent Graphic Services, 1973.
Cita MLAHelick, R. Martin. Elements of Preschool Playyards. Regent Graphic Services, 1973.
Warning: These citations may not always be 100% accurate.