Duggal. Elements of Environmmental Engineering.
Chicago-čujuhus (17. p.)Duggal. Elements of Environmmental Engineering.
MLA-čujuhus (9. p.)Duggal. Elements of Environmmental Engineering.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.