Thomas Behrendt Kevin J. Compton Erich Grädel Optimization Problems: Expressibility, Approximation Properties and Expected Asymptotic Growth of Optimal Solutions. 43-60 1992 conf/csl/1992 CSL db/conf/csl/csl92.html#BehrendtCG92 http://dx.doi.org/10.1007/3-540-56992-8_5