diff --git a/how_to b/how_to
index 23ae062..1c66364 100644
--- a/how_to
+++ b/how_to
@@ -1069,9 +1069,45 @@ Run studiotax on wine:
     wine ./StudioTax2017Install.exe /extract
     msiexec /i StudioTax.msi
 
-Easily switch to russian phonetic keyboard:
-    setxkbmap fr,ru -variant ,phonetic -option grp:shift_caps_toggle
-    man xkeyboard-config  # get list of possible toggles
+Xkb:
+    Easily switch to russian phonetic keyboard:
+        setxkbmap fr,ru -variant ,phonetic -option grp:shift_caps_toggle
+        man xkeyboard-config  # get list of possible toggles
+
+    Customisation notes:
+        - https://web.archive.org/web/20190724015820/http://pascal.tsu.ru/en/xkb
+        - https://gitlab.freedesktop.org/xkeyboard-config/xkeyboard-config/-/blob/master/docs/README.enhancing?ref_type=heads
+        - https://xkbcommon.org/doc/current/group__state.html#consumed-modifiers
+        - https://xkbcommon.org/doc/current/user-configuration.html
+        - https://xkbcommon.org/doc/current/user-configuration.html#autotoc_md16
+        - https://xkbcommon.org/doc/current/rule-file-format.html
+        - https://www.charvolant.org/doug/xkb/html/xkb.html
+        - https://medium.com/@damko/a-simple-humble-but-comprehensive-guide-to-xkb-for-linux-6f1ad5e13450
+        - https://github.com/isti115/dotfiles/blob/master/.config/xkb/symbols/Lenovo-Y50
+        - https://unix.stackexchange.com/a/101417
+        - https://delapouite.com/ramblings/xkb-walkthrough/
+        - https://github.com/xkbcommon/libxkbcommon/issues/17
+        - https://stackoverflow.com/a/45042841
+
+        Libxkbcommon is more flexible and modern in term of looking to ~/.xkb
+        and ~/.config/xkb as well as /usr/share/X11/xkb for config, but
+        unfortunately X11(?) isn't, and will only look into the system path.
+
+        Except for a single `custom` layout left free:
+            - https://blog.nemirwen.me/posts/fr-oss-ansi-xkb-layout
+            - https://gitlab.freedesktop.org/xkeyboard-config/xkeyboard-config/-/merge_requests/189/diffs
+
+        Also while libxkbcommon seems to rely more on rules files, X11 and so
+        setxkbmap seems to rely more on the xml descriptors. (supposition)
+        Also xorg's XKB rules syntax doesn't have %S or %H for recursive includes
+        `strace` is a very good tool to debug this mess.
+
+        Most people on the internet seem to rely on editing existing layout,
+        which feels icky to me.
+
+    Custom key type for Ctrl+Alt as AltGr:
+        - https://unix.stackexchange.com/a/187495
+
 
 Image/photo sorting with feh:
     feh --action1 'mv -v %F "/path/to/target/"%N' \