A group of thirteen drawings attributed to Pieter Brueghel the Elder was tested using the wavelet decomposition method.

The academy undertook minor refurbishments of the church and also there were projects for a new church prepared in drawings attributed to Ottaviano Mascherino (1536-1606).

He also purchased seven drawings attributed to Michelangelo from the Woodburn sale at Christie's in 1887 and gave them to the British Museum (five are still accepted as autograph).

My own favorite in this latter category is the 17th-century draftsman Jean de Saint-Igny, who has only now been identified as the author of more than 40 drawings previously attributed to Jacques Bellange.

The other image is a drawing, attributed to Pierre Puget (1620-94), of the elaborately decorated stern of the 100-gun warship Dauphin Royal (not the one mentioned above).

In the Monte Carlo auction, they are selling, along with the sketchbook, two drawings attributed to Leonardo da Vinci and an important painting by the 18th-century Venetian Francesco Guardi.

The computer program agreed with the Bruegel experts, grouping eight drawings attributed to Bruegel in one category and assigning the imitations to a separate pile.

"There's a long history of drawings attributed to Bruegel that we now know are not by him," he said.

Sixty-six paintings and eight drawings attributed to Gerstl are known, although it is possible he destroyed many more or that others could have been lost over the years.

About 80 to 100 drawings attributed to Bellange survive, though many of these would not be accepted by all authorities; there is no catalogue raisonné as yet.