Creswell, J. W. Research Design 4ed. Sage.
Chicago-čujuhus (17. p.)Creswell, John W. Research Design 4ed. Sage.
MLA-čujuhus (9. p.)Creswell, John W. Research Design 4ed. Sage.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.