--- a/NEWS Wed Apr 15 15:52:37 2009 +0200
+++ b/NEWS Thu Apr 16 10:11:34 2009 +0200
@@ -1,6 +1,14 @@
Isabelle NEWS -- history user-relevant changes
==============================================
+*** HOL ***
+
+* Class semiring_div now requires no_zero_divisors and proof of div_mult_mult1;
+theorems div_mult_mult1, div_mult_mult2, div_mult_mult1_if, div_mult_mult1 and
+div_mult_mult2 have been generalized to class semiring_div, subsuming former
+theorems zdiv_zmult_zmult1, zdiv_zmult_zmult1_if, zdiv_zmult_zmult1 and zdiv_zmult_zmult2.
+div_mult_mult1 is now [simp] by default. INCOMPATIBILITY.
+
New in Isabelle2009 (April 2009)
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