  The quasi-SU(3) symmetry, as found in shell model calculations, refers to the
dominance of the single particle plus quadrupole-quadrupole terms in the
Hamiltonian used to describe well deformed nuclei, and to the subspace relevant
in its diagonalization. It provides a very efficient basis truncation scheme.
It is shown that a small number of SU(3) coupled irreps, those with the largest
C_2 values within the direct product of the proton and neutron SU(3) irreps
with spin 0 and 1 (for even number of particles), and spin 1/2 and 3/2 for (for
odd number of nucleons), are enough to describe the low energy spectra and
B(E2) transition strengths of 21Ne, 23Na and 25Mg. A simple but realistic
Hamiltonian is employed. Results compare favorably both with experimental data
and with full shell model calculations. Limitations and possible improvements
of the schematic Hamiltonian are discussed.
