Cita APA (7a ed.)

(1968). Supplement to Soil Classification System: (7th Approximation). Soil Survey Staff, U. S. Department of Agriculture.

Cita Chicago Style (17a ed.)

Supplement to Soil Classification System: (7th Approximation). [s.n.]: Soil Survey Staff, U. S. Department of Agriculture, 1968.

Cita MLA (9a ed.)

Supplement to Soil Classification System: (7th Approximation). Soil Survey Staff, U. S. Department of Agriculture, 1968.