Ludger tom Ring art links 

Ludger tom Ring : The Delphic Sibyl

J. Paul Getty Museum, Los Angeles
Double Portrait, 1560

Louvre Museum Database, Paris
The Delphic Sibyl

Ludger tom Ring at the Metropolitan Museum of Art, New York City  
Christ Blessing, Surrounded by a Donor and His Family

Indianapolis Museum of Art, Indiana

 

Ludger tom Ring in the Art Renewal Center

Ludger tom Ring in the Web Gallery of Art  
Vases of Flowers, 1562

Wikimedia Commons Image Database  

Bildindex der Kunst und Architektur (in German)  
(a welcome screen is displayed for a couple of seconds before the search results appear)

California State University WorldImages Database  
Christ blessing with donors

Farbdia Archiv (Color Slide Archive) (in German)  
Thousands of photographs of fresco cycles and wall decorations in churches and other buildings in and around Germany.
Click "Galerie" for a normal overview; click "digilib" to zoom in.

 

Grove Dictionary of Art Online (excerpt)  

Union List of Artist Names (Getty Museum)  
Reference sheet with basic information about the artist and pointers to other references.