code: private PExp readConnectiveExpression() throws ParserException,
  			LexException
  	{
  		PExp exp = readImpliesExpression();
  		LexToken token = lastToken();
  
  		if (token.is(VDMToken.EQUIVALENT))
  		{
  			nextToken();
  			exp = AstFactory.newAEquivalentBooleanBinaryExp(exp, token, readConnectiveExpression());
  		}
  
  		return exp;
  	}
docs: Connectives Family. All (recursive) right grouping...