is mentioned

In prior sections: core fun 1 well fnd int 1 bool 1 int 2 list 1 mb collection sqequal 1 prog 1 mb tree rel 1 mb basic mb nat union num thy 1 mb list 1 mb label mb state machine mb list 2 mb automata 1 mb hybrid mb automata 2 mb automata 3 mb automata 4 mb structures