GENEVA (AP) -- A Zurich-based foundation says it will prove to the world Thursday that Leonardo Da Vinci painted an earlier version of the Mona Lisa.

The Mona Lisa Foundation, which has been working with the anonymous owners of the "Isleworth Mona Lisa," says that after 35 years of research, experts believe it predates the famed 16th-century masterpiece by about a decade.

The Isleworth painting -- likewise a portrait of a young woman with an enigmatic smile -- is slightly larger, was painted on canvas and has brighter colors than the famed Louvre Museum masterpiece painted on wood.

The group is presenting its findings to reporters Thursday in Geneva.

An accompanying book to be released by the foundation says the Isleworth Mona Lisa -- which was in storage for decades -- drew news headlines in the early 20th century.