1. [1] Babson, Eric; Barcelo, Hélène; De Longueville, Mark; Laubenbacher, Reinhard Homotopy theory of graphs, J. Algebr. Comb., Volume 24 (2006) no. 1, pp. 31-44
2. [2] Barcelo, Hélène; Capraro, Valerio; White, Jacob A. Discrete homology theory for metric spaces, Bull. Lond. Math. Soc., Volume 46 (2014), pp. 889-905
3. [3] Barcelo, Hélène; Kramer, Xenia; Laubenbacher, Reinhard; Weaver, Christopher Foundations of connectivity theory for simplicial complexes, Adv. Appl. Math., Volume 26 (2001), pp. 97-128
4. [4] Diestel, Reinhard Graph theory, Springer, Graduate Texts in Mathematics, Volume 173 (2000)
5. [5] Federer, Herbert Lectures on algebraic topology, Brown University (1962)