PAPASTAVRIDIS, Stavros. Imbeddings, immersions and integrability of characteristic classes,. Mathematica Scandinavica, Berkeley, CA, United States, v. 43, p. 177–184, 1978. DOI: 10.7146/math.scand.a-11773. Disponível em: https://journals.msp.org/mscand/article/view/1875. Acesso em: 25 jul. 2026.