Ryan, W. J. L. (1960). Price theory. Macmillan.
Lua i Stíl Chicago (17ú heag.)Ryan, William James Louden. Price Theory. London: Macmillan, 1960.
Lua MLA (9ú heag.)Ryan, William James Louden. Price Theory. Macmillan, 1960.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.