  We investigated the dispersion of nuclear spin waves in Nd$_2$CuO$_4$ by
using neutron spin-echo spectroscopy at millikelvin temperatures. Our results
show unambiguously the existence of dispersion of nuclear spin waves in
Nd$_2$CuO$_4$ at T = 30 mK. A fit of the dispersion data with the spin wave
dispersion formula gave the Suhl-Nakamura interaction range to be of the order
of 10 {\AA}.
