[EN] The aim of this paper is to prove a known fact that the digital line is cotractible. Hence we have that the digital space $({\bf Z}^{n}, \kappa^{n})$ is also cotractible where $({\bf Z}^{n}, \kappa^{n})$ is $n$ products ...

[EN] In the paper one defines topological invariants of type degree for morphisms in the category Top₍₂₎ of topological pairs of spaces and continuous single valued maps, which admit homological n-spheres as target and ...