References
- Bautista , R. and Smal⊘ , S. 1983 . Nonexistent cycles . Comm. Alg , 11 ( 16 ) : 1755 – 1767 .
- Butler , M. and Ringel , C.M. 1987 . On Auslander Reiten Sequences with few middle terms and applications to string algebras . Comm. Alg , 15 ( 1&2 ) : 145 – 179 .