"The Frankfurt Fair". web.archive.org. 2012-04-03. Archived from the original on 2012-04-03. Diakses tanggal 2022-06-05.Pemeliharaan CS1: Url tak layak (link)
"The Frankfurt Fair". web.archive.org. 2012-04-03. Archived from the original on 2012-04-03. Diakses tanggal 2022-06-05.Pemeliharaan CS1: Url tak layak (link)
"Universität Leipzig". web.archive.org. 2008-09-12. Archived from the original on 2008-09-12. Diakses tanggal 2022-06-05.Pemeliharaan CS1: Url tak layak (link)