BARFORT, John. Spengler - Klein: Introduction to business (New fourth edition) Me Craw- Hill Book Company 1955. Ledelse og Erhvervsøkonomi, [S. l.], v. 19, 1955. Disponível em: https://tidsskrift.dk/ledelseogerhvervsoekonomi/article/view/33544. Acesso em: 5 feb. 2026.