- Author: Jennifer Stepanek, Gary Appel, Melinda Leong, Michelle Turner Mangan, Mark Mitchell
- Language: English
- Year: 2006
- Author: Hannah Appel
- Language: English
- Year: 2023
- Author: Wolfgang Appel (editor), Werner Felisiak (editor)
- Language: German
- Year: 2015
- Author: Wolfgang Appel (editor), Werner Felisiak (editor)
- Language: German
- Year: 2015
- Author: Oscar Montelius, Carl Appel
- Language: German
- Year: 1885
- Author: Wolfgang Appel (editor), Werner Felisiak (editor)
- Language: German
- Year: 2011
- Author: Gustaf Retzius, Carl Appel
- Language: German
- Year: 1885
- Author: Carl Appel
- Language: German
- Year: 1882
- Author: Carl Appel
- Language: German
- Year: 1886