Using C-c C-c in a bibtex cleans the entry and generates a citation key.
If the author name includes non-ascii characters these are included in
the key, even though BibTeX does not accept this.

For example:
@Article{äöü21,
  author =          {æøå äöü},
  title =               {foo},
  journal =          {bar},
  year =               2021}



In GNU Emacs 27.1 (build 1, x86_64-w64-mingw32)
of 2020-08-21 built on CIRROCUMULUS
Repository revision: 86d8d76aa36037184db0b2897c434cdaab1a9ae8
Repository branch: HEAD
Windowing system distributor 'Microsoft Corp.', version 10.0.17134
System Description: Microsoft Windows 10 Enterprise (v10.0.1803.17134.2087)

Recent messages:
Checking 71 files in c:/Program Files (x86)/Emacs/emacs-27.1-x86_64/share/emacs/27.1/lisp/erc...
Checking 34 files in c:/Program Files (x86)/Emacs/emacs-27.1-x86_64/share/emacs/27.1/lisp/emulation...
Checking 180 files in c:/Program Files (x86)/Emacs/emacs-27.1-x86_64/share/emacs/27.1/lisp/emacs-lisp...
Checking 24 files in c:/Program Files (x86)/Emacs/emacs-27.1-x86_64/share/emacs/27.1/lisp/cedet...
Checking 59 files in c:/Program Files (x86)/Emacs/emacs-27.1-x86_64/share/emacs/27.1/lisp/calendar...
Checking 87 files in c:/Program Files (x86)/Emacs/emacs-27.1-x86_64/share/emacs/27.1/lisp/calc...
Checking 113 files in c:/Program Files (x86)/Emacs/emacs-27.1-x86_64/share/emacs/27.1/lisp/obsolete...
Checking 1 files in c:/Users/brel/AppData/Roaming/.emacs.d/lisp/dna-mode...
Checking for load-path shadows...done
Making completion list...

Configured using:
'configure --without-dbus --host=x86_64-w64-mingw32
--without-compress-install 'CFLAGS=-O2 -static''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY W32NOTIFY ACL GNUTLS LIBXML2
HARFBUZZ ZLIB TOOLKIT_SCROLL_BARS MODULES THREADS JSON PDUMPER LCMS2 GMP

Important settings:
  value of $LANG: DAN
  locale-coding-system: cp1252

Major mode: Lisp Interaction

Minor modes in effect:
  save-place-mode: t
  delete-selection-mode: t
  show-paren-mode: t
  recentf-mode: t
  global-auto-revert-mode: t
  cua-mode: t
  TeX-PDF-mode: t
  TeX-source-correlate-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(help-mode pp shadow sort mail-extr emacsbug message rmc puny dired
dired-loaddefs format-spec rfc822 mml mml-sec epa derived epg epg-config
gnus-util rmail rmail-loaddefs text-property-search time-date mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
saveplace delsel paren recentf tree-widget wid-edit autorevert
filenotify cua-base cus-start cus-load server tex-mik tex crm advice
texmathp finder-inf info tex-site package easymenu browse-url
url-handlers url-parse auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json subr-x map url-vars seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib tooltip eldoc electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel dos-w32 ls-lisp
disp-table term/w32-win w32-win w32-vars term/common-win tool-bar dnd
fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core term/tty-colors frame minibuffer cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote threads w32notify w32
lcms2 multi-tty make-network-process emacs)

Memory information:
((conses 16 100510 8583)
(symbols 48 10963 1)
(strings 32 33640 2227)
(string-bytes 1 1011136)
(vectors 16 16807)
(vector-slots 8 206002 13918)
(floats 8 44 213)
(intervals 56 279 0)
(buffers 1000 15))