I personally like <a href="http://www.math.msu.su/~fpm/eng/k01/k012/k01216h.htm">this</a> elegant but somewhat obscure (relatively) recent paper by Alekhnovich and Belov (MR1866477; <a href="http://www.emis.de/journals/FPM/rus/k01/k012/k01216h.htm">Russian version</a> is downloadable; it was written while <a href="http://www.math.ias.edu/~misha/">Misha</a> was still in Moscow).  Enjoy!