Question: Who wrote the episode directed by Jos Humphrey that had an original Canadian air date that was unknown and a United States original air date of August 27, 2011?
Schema: create table table_29087004_2 (written_by varchar, united_states_original_airdate varchar, directed_by varchar, canada_original_airdate varchar, PRIMARY KEY (written_by))
SQL: select written_by from table_29087004_2 where directed_by = "jos humphrey" and canada_original_airdate = "unknown" and united_states_original_airdate = "august 27, 2011"