  The residual torsion-free nilpotence of the commutator subgroup of a knot
group has played a key role in studying the bi-orderability of knot groups. A
technique developed by Mayland provides a sufficient condition for the
commutator subgroup of a knot group to be residually-torsion-free nilpotent
using work of Baumslag. In this paper, we apply Mayland's technique to several
genus one pretzel knots and a family of pretzel knots with arbitrarily high
genus. As a result, we obtain a large number of new examples of knots with
bi-orderable knot groups. These are the first examples of bi-orderable knot
groups for knots which are not fibered or alternating.
