Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE stadium ( id number, name text, home_games number, average_attendance number, total_attendance number, capacity_percentage number )
TABLE: CREATE TABLE injury_accident ( game_id number, id number, player text, injury text, number_of_matches text, source text )
TABLE: CREATE TABLE game ( stadium_id number, id number, season number, date text, home_team text, away_team text, score text, competition text )

### Question ###
How many different kinds of information sources are there for injury accidents?

### Accurate SQL ###

SELECT COUNT(DISTINCT source) FROM injury_accident