Cheronis, N. D. The study of the physical world. [Boston],1958: Houghton Mifflin.
Dyfyniad Arddull ChicagoCheronis, Nicholas D. The Study of the Physical World. [Boston],1958: Houghton Mifflin.
Dyfyniad MLACheronis, Nicholas D. The Study of the Physical World. [Boston],1958: Houghton Mifflin.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.