Here are a couple of PDF welding guides which may be of some use to some members.
Stick Welding Principles.
Basic Welding And Cutting Principles.

The Welding Of Aluminium and its Alloys

Introduction.
Contents.
Welding aluminium.
Welding metallurgy.
Material standards and alloys.
Preparation for welding.
Welding design.
TIG welding.
MIG welding.
Other welding processes.
Resistance welding.
Welding procedure and welder approval.
Weld defects and quality control.
Apendicies.
Bibliography.
Indexes.