Holton,C.A, & Sheehan,J. (1993). Peterson graph. Cambridge University press.
Dyfyniad Arddull ChicagoHolton,C.A, and Sheehan,J. Peterson Graph. Cambridge: Cambridge University press, 1993.
Dyfyniad MLAHolton,C.A, and Sheehan,J. Peterson Graph. Cambridge University press, 1993.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.