what are two groups who discovered america by crossing the atlantic before columbus? (not the vikings)

Long before America was discovered by Columbus, a band of Irish monks led by Saint Brenden visited Americas in sixth century. They traveled on ox-boats and returned after seven years. They reported that they have discovered a land full of vegetation, people believe that the land he mentioned was Newfoundland.

Some scholars say that before Vikings America was visited by Chinese travelers and also by visitors from Ice Age Europe and Africa.

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