Layard, R. (1972). Cost- benefit analysis. Penguin.
Lua i Stíl Chicago (17ú heag.)Layard, Richard. Cost- Benefit Analysis. New York: Penguin, 1972.
Lua MLA (9ú heag.)Layard, Richard. Cost- Benefit Analysis. Penguin, 1972.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.