In his famous (but unknown to me until recently) 1967 paper,* Richardson showed that the problem of deciding whether a one-variable subelementary expression (an expression involving +, -, *, exp, sin, composition, the constants log 2, pi, and all rational numbers, plus variables x_i) is negative is undecidable. This is a counterpoint to Tarski's decidability result on real closed fields (+, *, =, <). Many papers have improved on these results in some direction or another. In particular, I was wondering if anyone knew whether this (once?-)unsolved problem mentioned in the paper has been solved: Also, is there a good survey paper on this sort of work? There is a recent result of Laczkovich that generalizes Richardson (via Wang) by removing constants and substantially reducing composition, but I haven't seen anything remove the variable. * Daniel Richardson, "Some undecidable problems involving elementary functions of a real variable", Journal of Symbolic Logic 33:4 (1968), pp. 514-520.