  We find that single spin asymmetries in NRQCD are non-vanishing in general.
They are proportional to the imaginary parts of some non-perturbative matrix
elements. With statistics of about 10^6 identified J/psi's, or 10^5 identified
chi_2, it is possible to measure these imaginary parts even if they are an
order of magnitude smaller than the real parts. Such statistics are quite
reasonable at polarised HERA N and other future experiments.
