Petch, C. P. (1977). Points from letters: The magic puff-ball.
Dyfyniad Arddull ChicagoPetch, C P. Points From Letters: The Magic Puff-ball. 1977.
Dyfyniad MLAPetch, C P. Points From Letters: The Magic Puff-ball. 1977.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.