Asymptotic Formulae for the Coefficients of a Class of Modular Forms. Gunnar Dirdal — 1972 Mathematica Scandinavica
Congruences for the Fourier coefficients of certain modular forms. Gunnar Dirdal — 1976 Mathematica Scandinavica
Congruence properties for a class of arithmetical functions. Gunnar Dirdal — 1976 Mathematica Scandinavica