CC Madhya 20.363

avatāra-kāle haya jagate gocara
ei dui lakṣaṇe keha jānaye īśvara”
Word for word: 
avatāra-kāle — at the time of incarnation; haya — there is; jagate — in the world; gocara — information; ei dui lakṣaṇe — by these two characteristics, namely svarūpa and taṭastha; keha — some persons; jānaye — know; īśvara — the incarnation of the Supreme Lord.
Translation: 
“At the time of Their appearance, the incarnations of the Lord are known in the world because people can consult the śāstras to understand an incarnation’s chief characteristics, known as svarūpa and taṭastha. In this way the incarnations become known to great saintly persons.”