These are informal notes based on lectures given at various workshops and seminars. Use them with caution, as there
may be some errors due to oversight.

Combinatorial group theory based on
lectures given at HarishChandra Research Institute in December 2000
during the conference on Low Dimensional Topology and Geometry.
(10 pages, PS file.)

Monodromy of the KnizhnikZamolodchikov
equations and quantum groups notes of lectures given at the
workshop on Quantum Groups held at Ramanujan Institute, Chennai, during
March 2001. (8 pages, PS file.)

Hyperbolic groups based on lectures
given at the XIV Brazilian Topology Meet, Campinas, in July 2004.
(20 pages, PS file.)

Division algebras, Hopf invariant, and vector
fields.
Notes of lectures given at the 20th Annual Conference of the Ramanujan
Mathematical Society, Kozhikodu, in July 2005. (14 pages, ps file.)
Characteristic classes.
Based on lectures at the Advanced Instructional School on algebraic and
differential topology, held at ISI Kolkata, December 2005. (49 pages. ps file.)

K theory of toric manifolds.
Notes of lectures given at IIT Madras, Chennai, during December 2008January 2009.