German Ideology is located in the Collected Works of Karl Marx and Friedrich Engels pp. 19 through 539. While living in Barmen, Engels began making contact with Socialists in the Rhineland to raise money for Marx's publication efforts in Brussels. Source: Internet
Heinrich Gemkow et al., Friedrich Engels: A Biography p. 625. Having left Paris on 6 September 1844, Engels returned to his home in Barmen, Germany, to work on his The Condition of the Working Class in England, which was published in late May 1845. Source: Internet