diff --git a/SC2268.md b/SC2268.md
index 61dc2ba..08d1508 100644
--- a/SC2268.md
+++ b/SC2268.md
@@ -47,4 +47,5 @@ If you are targeting especially old shells, you can ignore this warning (or use
 ### Related resources:
 
 * [What exactly was the point of `[ "x$var" = "xval" ]`](https://www.vidarholen.net/contents/blog/?p=1035)?
-* [Wooledge Bash Pitfall #4](https://mywiki.wooledge.org/BashPitfalls#A.5B_.24foo_.3D_.22bar.22_.5D)
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+* [Wooledge Bash Pitfall #4](https://mywiki.wooledge.org/BashPitfalls#A.5B_.24foo_.3D_.22bar.22_.5D)
+* [Problems With the test Builtin: What Does -a Mean?](http://www.oilshell.org/blog/2017/08/31.html)
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