Notes on random reals
  The theory of random real numbers is exceedingly well-developed, and fascinating from many points of view. It is also quite challenging mathematically. The present notes are intended as no more than a gateway to the larger theory. They review just the most elementary part of the theory (bearing on Kolmogorov- and ML-randomness). We hope that the simple arguments presented here will encourage the enterprising student to examine richer treatments of the subject available elsewhere, notably, in Downey and Hirschfeldt (2010). 
Daniel Osherson and Scott Weinstein
cs.CC