Question: Don Barry Mason was the founder of the Psychedelic Shamanistic Institute (PSI), which other member that's Welsh, that died on 10 April 2016?
Sentence (from "Howard Marks"): Dennis Howard Marks (13 August 1945 – 10 April 2016) was a Welsh drug smuggler and author who achieved notoriety as an international cannabis smuggler through high-profile court cases.
Relevant evidence: Yes