the overworking of the negro, and sometimes the using up of his life in 7 years of labour, became a factor in a calculated and calculating system. It was no longer a question of obtaining from him a certain quantity of useful products. It was now a question of production of surplus labour itself". (Karl Marx, 1887 [2010]: 35, 244)
país: America
any: 1966
Yvert: 740a