  The Haldane gap material NENP exhibits anomalies in its Knight shift, far
infrared absorption and field-dependent gaps, which have been explained using
the staggered $g$-tensor that occurs due to the low crystal symmetry. We point
out that the low-temperature susceptibility is also anomalous and that a
consistent interpretation of all data may require consideration of the
Dzyaloshinskii-Moriya interaction.
