Elderton, W. P., & Johnson, N. L. (1969). Systems of frequency curves. Cambridge University.
Chicago-čujuhus (17. p.)Elderton, William Palin, juo Norman Lloyd Johnson. Systems of Frequency Curves. Cambridge: Cambridge University, 1969.
MLA-čujuhus (9. p.)Elderton, William Palin, juo Norman Lloyd Johnson. Systems of Frequency Curves. Cambridge University, 1969.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.