Popham, W. J., & Baker, E. L. (1970). Systematic instruction. Prentice-Hall.
Lua i Stíl Chicago (17ú heag.)Popham, W. James, agus Eva L. Baker. Systematic Instruction. Englewood Cliffs, N.J.: Prentice-Hall, 1970.
Lua MLA (8ú heag.)Popham, W. James, agus Eva L. Baker. Systematic Instruction. Prentice-Hall, 1970.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.