Art historians have long argued over whether the woman in the famed 16th-century portrait might have been Leonardo's companion, mother or even the artist himself.

But Deutsche Welle reported Veit Probst, director of the Heidelberg University Library, has announced there is strong evidence the enigmatic woman in the painting was Gherardini, the wife of merchant Francesco del Giocondo.

To back up his claim, Probst pointed to recently discovered notes dated October 1503 and scribbled in the margins of a book found in the library, confirming Lisa Gherardini was the model and her husband likely the one who commissioned the portrait, Deutsche Welle said.

The book was discovered by manuscript expert Armin Schlechter.

"There is no reason for any lingering doubts that this is another woman," Leipzig University art historian Frank Zollner told a German radio station. "One could even say that books written about all this in the past few years were unnecessary."