I am looking for a proof why the minor embedding problem (or minor graph search or minor testing) belongs to NP-complete problems. I would like to find a paper or in general an explanation that shows the relation to other NP-problems, e.g. how to reduce the search for the minor graph to another NP-complete problem.
Looking online I have found many articles that show specific cases of the problem that can be solved polynomially, but that is not what I am looking for.