Koekoek, R. (1969). The structure of papain: An X-ray diffraction study at 2.8Å resolution. V.R.B.-Offsetdrukkerij.
Lua i Stíl Chicago (17ú heag.)Koekoek, Roelof. The Structure of Papain: An X-ray Diffraction Study at 2.8Å Resolution. Groningen: V.R.B.-Offsetdrukkerij, 1969.
Lua MLA (8ú heag.)Koekoek, Roelof. The Structure of Papain: An X-ray Diffraction Study at 2.8Å Resolution. V.R.B.-Offsetdrukkerij, 1969.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.