diff --git a/SC1010.md b/SC1010.md
index d022d1e..7ba754b 100644
--- a/SC1010.md
+++ b/SC1010.md
@@ -35,3 +35,6 @@ In the example, `echo "$f" done` is the same as `echo "$f" "done"`, and the `don
 ### Exceptions
 
 If you're intentionally using `done` as a literal, you can quote it to make this clear to ShellCheck (and also human readers), e.g. instead of `echo Task is done`, use `echo "Task is done"`. This makes no difference to the shell, but it will silence this warning.
+
+From POSIX-2018, section "C.2.10 Shell Grammar," regarding the syntax, `if (false) then (echo x) else (echo y) fi`:
+https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xcu_chap02.html#tag_23_02_10