1. J. L. Alperin,Projective modules for SL(2, 2 n ) (to appear).
2. R. W. Carter,Simple groups of Lie type, London, John Wiley & Sons, 1972.
3. H. Enomoto, The characters of the finite symplectic groups Sp(4,q),q=2 f ,Osaka J. Math.,9 (1972), 75–94.
4. J. E. Humphreys, Projective modules for SL2(q),J. of Algebra,25 (1973), 513–518.
5. A. V. Jeyakumar, Principal indecomposable representations for the group SL(2,q),J. of Algebra,30 (1974), 444–458.