The class places no constraints on how you do your bibliography. It doesn’t care whether you are using the
chapterbib package with natbib or the per-chapter bibliography functionality provided by biblatex. If you
have per-chapter bibliographies, however, you must use the [chapterbib] class option. This
option lets the class know that you are using per-chapter bibliographies. Note that per-chapter
bibliographies should not be preceded by the \backmatter command, which should not be used at
all.
Please note that although bibliography entries must be single spaced, there must be a space between each entry. This parameter is set by your bibliography package and not by the class itself. If you are using natbib or biblatex these spacing parameters are set for you by the class. If you are using another package for your bibliography you are responsible for adjusting the relevant spacing parameters.