user: Question: With which association did Estribillo II run as Horse 1?
Columns: ['Year', 'City', 'Rider 1', 'Rider 2', 'Horse 1', 'Horse 2', 'Association']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1949.0, 'Rancagua', 'Ernesto Santos', 'José Gutiérrez', 'Vanidosa', 'Bototo', 'Temuco']
SQL:

assistant: SELECT "Association" FROM "Table" WHERE "Horse 1" = 'Estribillo II';