  These are notes on de Jong's proof of the period=index theorem over fields of
transcendence degree two. They are actually about the simplified proof sketched
by de Jong in the last section of his paper. These notes were meant as support
for my lectures at the summer school "Central Simple Algebras over Function
Fields" at the Universitat Konstanz between August, 26 and September, 1 2007
(other lectures on this subject were given by Philippe Gille, Andrew Kresch,
Max Lieblich, Tamas Szamuely and Jan Van Geel).
  No originality is intended (except perhaps a little in the proof of the Artin
splitting theorem). Various sources on which the material is based are
indicated in the notes.
  The reader should be warned that these notes have not been updated to reflect
developments in the subject which occurred after the end of the summerschool.
