Day, R. W. (2001). Soil testing manualprocedures, classiffication data, and sampling practices. McGraw-Hill.
Dyfyniad Arddull ChicagoDay, Robert W. Soil Testing Manualprocedures, Classiffication Data, and Sampling Practices. McGraw-Hill, 2001.
Dyfyniad MLADay, Robert W. Soil Testing Manualprocedures, Classiffication Data, and Sampling Practices. McGraw-Hill, 2001.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.