 Complete the following phrase:  Partizans supporters, known as Grobari Serbian Cyrillic: Гробари, Gravediggers or Undertakers, were formed in 1970. The origin of the nickname itself is uncertain, but an accepted theory is that it was given by their biggest rivals, the Red Star fans, referring to clubs mostly black colours which were similar to the uniforms of cemetery undertakers. The other theory says that the name arrives from the Partizans stadium street name, Humska humka meaning grave mound, in actuality named after medieval land of Hum. The first groups of organized Partizan supporters began to visit the JNA stadium in the late 1950s. Partizans participation in the 