diff --git a/TODO b/TODO
index 86d515c..c049a84 100644
--- a/TODO
+++ b/TODO
@@ -15,8 +15,5 @@ vault checksum: add keysigs as well
 
 Add newlines to headers in define.h, so strlen() later catches the whole length.
 
-Check is_utf8 license.
-  also found in https://gd.meizo.com/_files/lpc/ext/utf8.c
-
 c++ destructor double free mess
 
diff --git a/libpcp/z85.c b/libpcp/z85.c
index 62d6bc7..e7446e9 100755
--- a/libpcp/z85.c
+++ b/libpcp/z85.c
@@ -35,6 +35,9 @@ static char *begins[] = {
 
 
 
+/* via http://stackoverflow.com/a/1031773, slightly modified,
+   licensed under CC-BY-SA, written by Christoph
+*/
 uint8_t is_utf8(const byte *bytes) {
   if( (// non-overlong 2-byte
        (0xC2 <= bytes[0] && bytes[0] <= 0xDF) &&