Croatian Black Hole School 2010 lecture notes on IMBHs in GCs
  Black holes are fascinating objects. As a class of solutions to the Einstein
equations they have been studied a great deal, yielding a wealth of theoretical
results. But do they really exist? What do astronomers really mean when they
claim to have observational evidence of their existence? To answer these
questions, I will focus on a particular range of black-hole masses,
approximately from 100 to 10000 solar masses. Black holes of this size are
named Intermediate Mass Black Holes (IMBHs) and their existence is still
heavily disputed, so they will be perfect for illustrating the observational
challenges faced by a black hole hunter
