Basel Zoo euthanises star bull elephant - SWI

Basel Zoo Review: From Caging Humans to Saving Rhinos

Elephant bull Tusker has passed away

Call to end elephant captivity - WRS

Baby elephant dies rejected by family at swedish zoo - Elephant News

Elephants in the Zoo Basel – Upali.ch

African Elephant

Sanctuary - The Atavist Magazine

Basel Zoo euthanises star bull elephant - SWI

Editorial: L.A. Zoo's elephant star Billy deserves to retire - Los Angeles Times