  Circular layouts are a popular graph drawing style, where vertices are placed
on a circle and edges are drawn as straight chords. Crossing minimization in
circular layouts is \NP-hard. One way to allow for fewer crossings in practice
are two-sided layouts that draw some edges as curves in the exterior of the
circle. In fact, one- and two-sided circular layouts are equivalent to one-page
and two-page book drawings, i.e., graph layouts with all vertices placed on a
line (the spine) and edges drawn in one or two distinct half-planes (the pages)
bounded by the spine. In this paper we study the problem of minimizing the
crossings for a fixed cyclic vertex order by computing an optimal $k$-plane set
of exteriorly drawn edges for $k \ge 1$, extending the previously studied case
$k=0$. We show that this relates to finding bounded-degree maximum-weight
induced subgraphs of circle graphs, which is a graph-theoretic problem of
independent interest. We show \NP-hardness for arbitrary $k$, present an
efficient algorithm for $k=1$, and generalize it to an explicit \XP-time
algorithm for any fixed $k$. For the practically interesting case $k=1$ we
implemented our algorithm and present experimental results that confirm the
applicability of our algorithm.
