diff --git a/SC1037.md b/SC1037.md
index a7cbbfa..5fc4257 100644
--- a/SC1037.md
+++ b/SC1037.md
@@ -36,3 +36,4 @@ dash -c 'set a b c d e f g h i j; echo $10 ${1}0' # WRONG: j a0
 * [BashFaq: How can I access positional parameters after $9?](https://mywiki.wooledge.org/BashFAQ/025)
 * [StackOverflow: How to handle more than 10 parameters in shell
 ](https://stackoverflow.com/questions/4912733/how-to-handle-more-than-10-parameters-in-shell)
+* [Autoconf Manual: Shell Substitutions](https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/html_node/Shell-Substitutions.html) - documents some non-POSIX older shells too