 The "Bella Principessa" remains locked in a vault in a secret Swiss location.According to Kemp and Cotte, the sheet was cut from a Milanese vellum book, "La Sforziada", in Warsaw, which celebrates the marriage in 1496 of Galeazzo Sanseverino with Bianca, the illegitimate daughter of Ludovico Sforza, Leonardo's employer.It has subsequently been exhibited in Urbino, Monza and Nanjing; and a facsimile edition of the portrait and the book in Warsaw has been published.