Engert, M. (1969). Problems of Long-term Planning in the German Democratic Republic. The Institute of National Planning.
Chicago-viite (17. p.)Engert, Manfred. Problems of Long-term Planning in the German Democratic Republic. Cairo: The Institute of National Planning, 1969.
MLA-viite (9. p.)Engert, Manfred. Problems of Long-term Planning in the German Democratic Republic. The Institute of National Planning, 1969.