On sets of first-order formulas axiomatizing representable relation   algebras
  This is the author's 2004 Master's thesis at Iowa State University, done under the supervision of Roger D. Maddux. It provides a background in relation algebras. Three results from the literature are demonstrated in full: (i.) RRA is a variety. (ii.) RRA is not finitely based. (iii.) Any equational basis for RRA has infinitely many variables. We also give an elementary proof of Birkoff's variety theorem. 
Jeremy F. Alm
math.LO math.RA