William Powell. (2003). Drawing Trees. Walter Foster Publishing.
Chicago-čujuhus (17. p.)William Powell. Drawing Trees. Walter Foster Publishing, 2003.
MLA-čujuhus (9. p.)William Powell. Drawing Trees. Walter Foster Publishing, 2003.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.