  We study the Optimal Linear Arrangement (OLA) problem of Halin graphs, one of
the simplest classes of non-outerplanar graphs. We present several properties
of OLA of general Halin graphs. We prove a lower bound on the cost of OLA of
any Halin graph, and define classes of Halin graphs for which the cost of OLA
matches this lower bound. We show for these classes of Halin graphs, OLA can be
computed in O(n log n), where n is the number of vertices.
