Elderton, W. P., & Johnson, N. L. (1969). Systems of frequency curves. Cambridge University.
Dyfyniad Arddull ChicagoElderton, William Palin, and Norman Lloyd Johnson. Systems of Frequency Curves. Cambridge: Cambridge University, 1969.
Dyfyniad MLAElderton, William Palin, and Norman Lloyd Johnson. Systems of Frequency Curves. Cambridge University, 1969.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.