anchor.diff:      (:h3 "Slot configuration")
       (:p "Slots store values that can be either accessed (get) or changed
   (set). Setting new values for slots allows many possibilities of customization.
  -For instance, keyboard layouts vary across the world. The slot " (:code
  -"hints-alphabet") " has the default value of " (:code
  -"ABCDEFGHIJKLMNOPQRSTUVWXYZ" ) ". If the user has an American keyboard, they can
  -do:")
  +For instance, keyboard layouts vary across the world. The slot "
  +        (:code "hints-alphabet")
  +        " has the default value of "
  +        (:code "ABCDEFGHIJKLMNOPQRSTUVWXYZ")
  +        ". If the user has an American keyboard, they can do:")
       (:ol
        (:li "Execute command " (command-markup 'describe-slot) ";")
        (:li "Type " (:code 'hints-alphabet)";")
  
positive.code: add the following to your configuration:")
      (:ul
       (:li "vi bindings:"
        (:pre (:code "
  \(define-configuration buffer
    ((default-modes (append '(vi-normal-mode) %slot-default%))))")))
       (:li "Emacs bindings:"
        (:pre (:code "
  \(define-configuration buffer
    ((default-modes (append '(emacs-mode) %slot-default%))))"))))
      (:p "You can create new scheme names with " (:code "keymap:make-scheme-name")
          ".  Also see the " (:code "scheme-name") " class and the "
          (:code "define-scheme") " macro.")
       (:p "To extend the bindings of a specific mode, you can extend the mode with "
           (:code "define-configuration") " and extend its binding scheme with "
           (:code "define-scheme") ". For example:")
       (:pre (:code "
  \(define-configuration base-mode
    ((keymap-scheme
      (define-scheme (:name-prefix \"my-base\" :import %slot-default%)
        scheme:vi-normal
        (list \"g b\" (make-command switch-buffer* ()
                      (switch-buffer :current-is-last-p t)))))))"))
       (:p "The " (:code "override-map") " is a keymap that has priority over
  all other keymaps.  By default, it has few bindings like the one
  for " (:code "execute-command") ".  You can use it to set keys globally:")
      (:pre (:code "
  
negative.code:     (:p "Note that the last search engine is the default one. For example, in
  order to make python3 the default, the above code can be slightly modified as
  follows.")
      (:pre (:code "
  \(defvar *my-search-engines*
    (list
     '(\"doi\" \"https://dx.doi.org/~a\" \"https://dx.doi.org/\")
  