engert, m. (1964). classification of industries in social countries. the institute of national planning.
শিকাগো স্টাইল (17 তম সংস্করণ) উদ্ধৃতিengert, manfred. Classification of Industries in Social Countries. cairo: the institute of national planning, 1964.
M.L.A (9 ম সংস্করণ) উদ্ধৃতিengert, manfred. Classification of Industries in Social Countries. the institute of national planning, 1964.