1. A general theory of invariants for meromorphic differential equations. I. Formal invariants;Balser;Funkcial. Ekvac.,1979
2. A general theory of invariants for meromorphic differential equations. II. Proper invariants;Balser;Funkcial. Ekvac.,1979
3. A general theory of invariants for meromorphic differential equations. III. Applications;Balser;Houston J. Math.,1980
4. Birkhoff invariants and Stokes' multipliers for meromorphic linear differential equations;Balser;J. Math. Anal. Appl.,1979
5. On the reduction of connection problems for differential equations with an irregular singular point to ones with only regular singularities, I;Balser;SIAM J. Math. Anal.,1981