Task: Question Answering
Input (English): Context: German academics believe they have solved the centuries-old mystery of the "Mona Lisa" in Leonardo ad Vinci's famous portrait . Lisa Gherardini, the wife of a wealthy Florentine merchant, Francesco del Giocondo, has long been seen as the most likely model for the sixteenth-century painting. Art historians have wondered whether the smiling woman may actually have been da Vinci's lover or mother, or the artist himself. Now experts at the prefix = st1 /HeidelbergUniversitylibrary say old notes made in a book by its owner in October, 1503, confirm that Lisa del Giocondo was indeed the model for the famous portrait in the world. "All doubts about the identity of the Mona Lisa have been removed by a discovery by Dr. Armin Schlechter," the library said in a statement on Monday. "Until then, only 'scant evidence' from sixteenth-century documents had been available. These had left lots of room for doubt, and many different identities were put forward." The comments compare Leonardo to the ancient Greek artist Apelles, and say he was working on three paintings at that time, one of which was a portrait of Lisa del Giocondo. Art experts say the Heidelbergdiscovery is a break-through, and the earliest mention linking the merchant's wife to the portrait. Before this discovery the earliest link dated from around 1550, and was made by Italian official Giorgio Vasari, the library said, adding that there had been doubts about Vasari's reliability. The Heidelbergnotes were actually discovered over two year's ago in the library by Schlechter, a spokeswoman said. Although the findings were published in the library's catalogue, they were not widely publicized, and received little attention until a German broadcaster decided to do some recording there, she said. 
 Question: Who discovered the Heidelbergnotes?
Output (English): dr. armin schlechter.