<|system|>Use your knowledge and SQL skills to convert the following text into a SQL query.
Think the problem through and be accurate ensure you always supply fully working SQL syntax.

SQL Statments should be wrapped in <codestart type="sql"> and </codeend> tags.

Example output:
<codestart type="sql">SELECT * FROM table_name;</codeend>
<codestart type="sql">SELECT column_name FROM table_name WHERE column_name = 'value';</codeend><|end|><|user|>What source has a race winner of ben adriaenssen / ben van den bogaart, and the gp winner of ben adriaenssen / ben van den bogaart, for the date of 1 april?

SQL Table Create Statement:
CREATE TABLE table_name_8 (source VARCHAR, date VARCHAR, race_winners VARCHAR, gp_winner VARCHAR)<|end|><|assistant|><codestart type="sql">SELECT source FROM table_name_8 WHERE race_winners = "ben adriaenssen / ben van den bogaart" AND gp_winner = "ben adriaenssen / ben van den bogaart" AND date = "1 april"</codeend><|end|>