The following is the introductory section of a paper collecting some of my mathematical thoughts of the last years. Some problems are still open, the literature about this specific subject is very scarce.
Any comment is heartly welcome.
Neumann, Halmos et al. Only for such B condition i is really distinctive. Stelle der Bestimmtheit . During the last decades these notions were not used very consistently, and the situation becomes worse, if systems of differential equations are considered, which stem from nth order linear differential equations. Using the above cited result of Hille's we see that of the three Fuchsian singularities 0,1 and infinity of this differential equation all are regular but only two are Stellen der Bestimmtheit .