  We show how the high order finite element spaces of differential forms due to
Raviart-Thomas-N\'edelec-Hiptmair fit into the framework of finite element
systems, in an elaboration of the finite element exterior calculus of
Arnold-Falk-Winther. Based on observations by Bossavit, we provide new low
order degrees of freedom. As an alternative to existing choices of bases, we
provide canonical resolutions in terms of scalar polynomials and Whitney forms.
