user: Question: Which women's doubles happened after 1987 and a women's single of Astrid van der Knaap?
Columns: ['Year', "Men's singles", "Women's singles", "Men's doubles", "Women's doubles", 'Mixed doubles']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1965.0, 'Otto Hecker', 'Peggy Brixhe', 'Fernando Pinto Vitor P. Alves', 'Isabel Salema Peggy Brixhe', 'Fernando Pinto Peggy Brixhe']
SQL:

assistant: SELECT "Women's doubles" FROM "Table" WHERE "Year" > 1987.0 AND "Women's singles" = 'Astrid van der Knaap';