The validity of mass functions for the central stars of planetary nebulae

It is commonly assumed that the distribution of masses for the central stars of planetary nebulae is strongly peaked about M-CS congruent to 0.6 M.. Such a mass function is similar to that deduced for white dwarfs. We show in the following however, that certain of the procedures used to evaluate N(M-CS) are seriously flawed and assume a nebular mass M-NEB that is probably inappropriate. At the very least, the uncertainty in M-NEB casts doubts upon the utility of these procedures, while the deduced functions N(M-CS) may be in error.