diff --git a/README.md b/README.md
index 22c1033..aef7b37 100644
--- a/README.md
+++ b/README.md
@@ -1640,6 +1640,7 @@ Equivalents to `Array`'s `.map(..)`, `.filter(..)` and `.reduce(..)` but return
 generators that yield the handler return values.
 
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+XXX doc all differences (revise)
 XXX .reduce(..) can return a non-iterable -- test and document this case...
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