Deletion of Northern Ireland Sign Language

Comment: I had referred to the http://www.global-lingo.com/interpreting-services/british-sign-language.html global-lingo.com page not just because it mentions NISL, but because it claims to "offer interpreters trained in" it. Another document I found is this http://www.belb.org.uk/publications/351.pdf school publication, which claims that its students "are also taught Northern Ireland Sign Language (NISL)" (pg. 33). Finally, I may have also found a source which qualifies under  and confirms the contentious status of NISL: ''Topics in Signed Language Interpreting: Theory And Practice'' by Terry Janzen, specifically pages http://books.google.com/books?id=ylfJtF3vQUwC&printsec=frontcover#PPA256,M1 256 and http://books.google.com/books?id=ylfJtF3vQUwC&printsec=frontcover#PPA265,M1 265, which quote a primary source written by http://www.bebo.com/Profile.jsp?MemberId=18322636 Shane O Heorpa (can't find it online). Is that source sufficient for retaining the article
Stance: comment
Cited policy: Wikipedia:Reliable sources (WP:RS)