human
Considering the provided database schema and associated query, produce SQL code to retrieve the answer to the query. 
###Database Schema: Year, Men's singles, Women's singles, Men's doubles, Women's doubles, Mixed doubles
###Question: Which women's doubles happened after 1987 and a women's single of astrid van der knaap?
gpt
SELECT Women's doubles FROM table WHERE Year > 1987 AND Women's singles = astrid van der knaap