H.-J. Kreowski, F. Orejas, et H. Ehrig, « Correctness of horizontal and vertical composition for implementation concepts based on constructors and abstractor », Rev. mat. complut., vol. 10, nᵒ 2, p. 365, janv. 1997, doi: 10.5209/rev_REMA.1997.v10.n2.17446.