https://tech.tiq.cc/2013/10/how-to-set-up-the-baikal-carddav-and-caldav-server-with-nginx-on-debian/ https://tech.tiq.cc/2013/10/how-to-set-up-the-baikal-carddav-and-caldav-server-with-nginx-on-debian/ http://ntbab.dyndns.org/apache2-default/seite/carddavproviderCE.html