Essays on representations and automorphic forms by Bill Casselman
These are a series of relatively short and selfcontained essays.
padic groups
Notes on the tree of SL(2) and its applications in analysis:

Notes on spherical functions
Written to accompany a reprinting of Ian Macdonald's book
on spherical functions on a padic group,
originally published in Madras and difficult to locate. The book
will indeed be reprinted in the series of lecture notes in mathematics,
but with no contribution from me.

Local quadratic reciprocity

The structure of GL(N)
Real groups
 Structure
 Representations
Automorphic forms

Automorphic forms for SL(2)
Root systems
Coxeter groups
Real analysis
Topological vector spaces and linear operators
Algebra
Quadratic forms
Miscellaneous
