CREATE TABLE table_20542 ("Species" TEXT, "Indole" TEXT, "Methyl Red" TEXT, "Voges-Proskauer" TEXT, "Citrate" TEXT)

What are the results for testing the species with voges-proskauer when citrate yields a positive result?
SELECT "Voges-Proskauer" FROM table_20542 WHERE "Citrate" = 'Positive'
SELECT "Voges-Proskauer" FROM "table_20542" WHERE "Citrate" = 'Positive'