user: Question: What is the Copa Libertadores 1999 result for team Vasco, which made the Group stage in the Copa Mercosur 1999?
Columns: ['Team', 'Copa Libertadores 1999', 'Copa Mercosur 1999', 'Copa CONMEBOL 1999', 'Intercontinental Cup 1999']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Corinthians', 'Quarterfinals', 'Quarterfinals', 'Did not qualify', 'N/A']
SQL:

assistant: SELECT "Copa Libertadores 1999" FROM "Table" WHERE "Copa Mercosur 1999" = 'Group stage' AND "Team" = 'Vasco';