diff --git a/README.md b/README.md
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@@ -12,7 +12,7 @@ Category Theory for Programmers
 **[Purchase now in full-color hardcover print on blurb.com](http://www.blurb.com/b/9008339-category-theory-for-programmers)**  
 Publish date: 21 October, 2018. Based off release tag [v1.0.0](https://github.com/hmemcpy/milewski-ctfp-pdf/releases/tag/v1.0.0). See [errata](errata.md) for changes and fixes since print.
 
-This is an *unofficial* PDF version of "Category Theory for Programmers" by Bartosz Milewski, converted from his [blogpost series](https://bartoszmilewski.com/2014/10/28/category-theory-for-programmers-the-preface/).
+This is an *unofficial* PDF version of "Category Theory for Programmers" by Bartosz Milewski, converted from his [blogpost series](https://bartoszmilewski.com/2014/10/28/category-theory-for-programmers-the-preface/) (with permission!)
 
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