That piece of canvas has been causing a lot of morbid curiosity. Since ever, artists and scientists have been puzzled by the identity of Mona Lisa (La Gioconda), the mysterious woman in Leonardo da Vinci's painting. Leonardo never made any notes about the model's identity himself, and this triggered the mystery.

All kinds of theories have been emitted. Many researches pointed towards the Florentine Lisa Gherardini, died on July 15, 1542, not a noblewoman or a princess but a family woman. But Gherardini, born in 1479 and married with a rich silk merchant, Francesco del Giocondo, has been strongly contested as being the woman from the painting.

She is connected to the painting because Giorgio Vasari, a 16th-century artist and Leonardo and other artists' biographer, explained that da Vinci made the portrait of del Giocondo's wife. The Florentine Francesco del Giocondo was a businessman, neighbor and friend of the artist's father, Piero da Vinci.

A research made at German University of Heidelberg has finally settled the issue: the woman is Lisa del Giocondo, the wife of Francesco del Giocondo, as revealed by book-margin notes written by Vasari.

The finding of a Heidelberg University library manuscript expert confirms what has been just a suspicion: "La Gioconda" is indeed the del Giocondo's wife.

In 1550, the Italian writer Giorgio Vasari pointed to del Giocondo and also dated the painting between 1503 and 1506. Still, Vasari relied on anecdotal proofs and he was doubted about the identification.

To complicate the issue, vague references in 1517, 1525, and 1540 lead to other identities.

"One possibility discussed is the presentation of a fictitious likeness of a woman; Leonardo's female ideal," the Heidelberg team noted.

Now, the Heidelberg library expert Armin Schlechter has confirmed the identity of the mysterious woman relying on a copy of the works of Roman philosopher Cicero.

Agostino Vespucci, a Florentine official and friend of Leonardo's, wrote on the margins of the copy, in October 1503, that da Vinci was making a portrait of Lisa del Giocondo.

"All doubts as to the identity of the Mona Lisa are eliminated (by) one source," wrote the Heidelberg team, who found this actually in 2005, but it was made public last week.