is mentioned by

Thm* b1,b2:. b1=b2 b1 = b2	[assert_of_eq_bool_iff_equal_bool]
Thm* b:. b b=false = false	[assert_of_bool_eq_bfalse_false]
Thm* P:. P P = false	[not_assert_iff_bfalse]
Thm* P:. P P = true	[assert_iff_btrue_rw]
Thm* P:. P P = true	[assert_iff_btrue]

In prior sections: core well fnd int 1 bool 1