David A. Mix Barrington Neil Immerman Clemens Lautemann Nicole Schweikardt Denis Thérien First-order expressibility of languages with neutral letters or: The Crane Beach conjecture. 101-127 2005 70 J. Comput. Syst. Sci. 2 http://dx.doi.org/10.1016/j.jcss.2004.07.004 db/journals/jcss/jcss70.html#BarringtonILST05