A Remark on Normal Derivations of Hilbert-Schmidt Type. B.P. Duggal — 1991 Monatshefte für Mathematik
Functional Equations and Linear Transformations. IV. Interpolation. B.P. Duggal — 1978 Mathematische Annalen
Functional equations and linear transformations - permutability and inversion. (Short Communication). B.P. Duggal — 1978 Aequationes mathematicae
Weyl's Theorem for a Generalized Derivation and an Elementary Operator B.P. Duggal — 2002 Matematički Vesnik
Subspace gaps and Weyl's theorem for an elementary operator. Duggal, B.P. — 2005 International Journal of Mathematics and Mathematical Sciences
Putnam-Fuglede theorem and the range-kernel orthogonality of derivations. Duggal, B.P. — 2001 International Journal of Mathematics and Mathematical Sciences