“…However, this natural necessary condition of deg D > 2g X − 2 is not sufficient for the existence of cone spherical metrics ( [33]). In this case Question 1.1 has been open over 20 years although many mathematicians had attacked or have been investigating it by using various methods and obtained a good understanding of the question ( [34,35,11,5,13,14,15,16,12,7,25,26,10,30,23]). Then we list some of the known results which are relevant to this manuscript.…”