National Fertilizer Development Center. (1973). Fertilizer trends. Washington, D.C: National Fertilizer Development Center.
Chicago Style aipamenaNational Fertilizer Development Center. Fertilizer Trends. Washington, D.C: National Fertilizer Development Center, 1973.
MLA aipamenaNational Fertilizer Development Center. Fertilizer Trends. Washington, D.C: National Fertilizer Development Center, 1973.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.