"Chabrier (2005)"
!#
!# "The Initial Mass Function: from Salpeter 1955 to 2005",
!# in "The Initial Mass Function 50 years later", Corbelli et al. (eds.), 
!# Astrophysics and Space Science Library, vol. 327, p. 41.
!# Revised version of the IMF in Chabrier (2003).
!# Analytical expression in "mod_IMF.f90".
