diff --git a/README.md b/README.md
index 089a14a..92643f0 100644
--- a/README.md
+++ b/README.md
@@ -348,3 +348,6 @@ See file `LICENSE` for a more detailed description of its terms.
 [clib]: https://github.com/clibs/clib
 [term]: https://github.com/bpkg/term
 [json]: http://json.org/example
+[shell features]: https://www.gnu.org/software/bash/manual/html_node/Basic-Shell-Features.html
+[special parameters]: https://www.gnu.org/software/bash/manual/html_node/Special-Parameters.html
+[shell expansions]: https://www.gnu.org/software/bash/manual/html_node/Shell-Expansions.html