is mentioned by

Thm* x:Label, ls:Label List. x ls (x ls)	[assert_lbls_member]
Thm* l1,l2:Label. l1 = l2 l1 = l2	[eq_lbl_iff]

In prior sections: core well fnd int 1 bool 1 fun 1 int 2 list 1 rel 1 mb basic mb nat num thy 1 mb list 1

Try larger context: GenAutomata