Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
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?

### Inputs:
table_name: table, columns: ['Date', 'Place', 'Race winners', 'GP winner', 'Source']

### Response:
SELECT Source FROM table WHERE Race winners = ben adriaenssen / ben van den bogaart AND GP winner = ben adriaenssen / ben van den bogaart AND Date = 1 april