Não informado. (1972). Shell in agriculture. Shell International Chemical Company.
Lua i Stíl Chicago (17ú heag.)Não informado. Shell in Agriculture. London: Shell International Chemical Company, 1972.
Lua MLA (8ú heag.)Não informado. Shell in Agriculture. Shell International Chemical Company, 1972.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.