Where is the first day cover cancellation for the 3 April 2008 IIHF World Championships, Quebec City stamp?
create table table_11900773_6 (first_day_cover_cancellation varchar, date_of_issue varchar, theme varchar, PRIMARY KEY (first_day_cover_cancellation))
select first_day_cover_cancellation from table_11900773_6 where date_of_issue = "3 april 2008" and theme = "iihf world championships, quebec city"