00475nam a2200133Ia 4500082001900000100003500019245013400054260003400188300001400222490003900236500000500275700003200280700002900312  a515.35bK21.DI  aKauffman, Robert M. and Others  aDeficiency index problem for powers of ordinary differential expressionsbcBy Robert M. Kauffman, Thomas T. Reed and Anton Zettl  aBerlinbSpringer-Verlagc1977  avi, 112p.  aLecture notes in Mathematicsv 621  a  aReed, Thomas T. ; jt. auth.  aZettl, Anton ; jt. auth.