Horn, K. H. (1967). Productivity , Concepts and Measurement. The Institute of National Planning.
Lua i Stíl Chicago (17ú heag.)Horn, Karl Heinz. Productivity , Concepts and Measurement. Cairo: The Institute of National Planning, 1967.
Lua MLA (9ú heag.)Horn, Karl Heinz. Productivity , Concepts and Measurement. The Institute of National Planning, 1967.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.