static L<TripleRef<Symbol>> ai_thoughtSpace_query(Symbol a, Symbol b, Symbol c, AbstractThoughtSpace ts) {
  L<TripleRef<Symbol>> l = null;
  if (!isDollarVar(a)) l = shortestListUnlessNull2(l, ts.get(a, 0));
  if (!isDollarVar(b)) l = shortestListUnlessNull2(l, ts.get(b, 1));
  if (!isDollarVar(c)) l = shortestListUnlessNull2(l, ts.get(c, 2));
  ret l;
}