@Override
 public ElkSubClassOfAxiom getPremise(int index, ElkObject.Factory factory) {
   checkPremiseIndex(index);
   int first = index, second = index + 1;
   if (second == expressions_.size()) {
     second = 0;
   }
   return factory.getSubClassOfAxiom(expressions_.get(first), expressions_.get(second));
 }
 @Override
 public ElkEquivalentClassesAxiom getConclusion(ElkObject.Factory factory) {
   return factory.getEquivalentClassesAxiom(expressions_);
 }