BERLIN — A researcher has uncovered evidence that apparently confirms the identity of the woman behind the Mona Lisa's iconic smile, Germany's University of Heidelberg says.

She is Lisa del Giocondo, wife of Florentine businessman Francesco del Giocondo, according to notes written in the margins of a book by a friend of Leonardo da Vinci as the artist worked on the masterpiece, the school said Monday.

The discovery, by a Heidelberg University library manuscript expert, appears to confirm what has long been suspected. It is also an answer that has been in plain view for centuries: the Mona Lisa is known as La Gioconda in Italian.

Del Giocondo was first named as the person in the painting by Italian writer Giorgio Vasari in 1550, who also dated the work at between 1503 and 1506, the university said.

But because Vasari relied on anecdotal evidence, there was always doubt about the identification, and Leonardo is not known to have made any notes about the model's identity.

Compounding the mystery, vague references in 1517, 1525 and 1540 point to other identifications.

But the find by Heidelberg library expert Armin Schlechter settles the matter, according to the university.

In a copy of the works of Roman philosopher Cicero, a Florentine official and friend of Leonardo wrote in the margins that da Vinci was working on a portrait of Lisa del Giocondo. The friend, Agostino Vespucci, dated his notes October 1503, also helping pin down when Leonardo worked on the painting. The discovery was made in 2005, but was not widely known until a German radio station reported it last week.