Maas, H. S., & Kuypers, J. A. (1974). From thirty to seventy. Jossey-Bass.
Lua i Stíl Chicago (17ú heag.)Maas, Henry S., agus Joseph A. Kuypers. From Thirty to Seventy. San Francisco: Jossey-Bass, 1974.
Lua MLA (9ú heag.)Maas, Henry S., agus Joseph A. Kuypers. From Thirty to Seventy. Jossey-Bass, 1974.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.