  In this contribution, we present the cluster shell model which is analogous
to the Nilsson model, but for cluster potentials. Special attention is paid to
the consequences of the discrete symmetries of three alpha-particles in an
equilateral triangle configuration. This configuration is characterized by a
special structure of the rotational bands which can be used as a fingerprint of
the underlying geometric configuration. The cluster shell model is applied to
the nucleus 13C.
