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

### Instruction:
Which 1997's accompanying 1991 was a when the tournament was the australian open?

### Inputs:
table_name: table, columns: ['Tournament', '1989', '1990', '1991', '1992', '1993', '1994', '1995', '1996', '1997', 'Career W–L']

### Response:
SELECT 1997 FROM table WHERE 1991 = a AND Tournament = australian open