Question: How many laboratory tests verified da Vinci's "Lady with an Ermine"?
About the article "Lady with an Ermine", section "Conservation".

Candidate passages:
White ferrets were favored in the Middle Ages for the ease in seeing them in thick undergrowth.
Leonardo da Vinci's painting "Lady with an Ermine" is likely mislabelled; the animal is probably a ferret, not a stoat, (for which "ermine" is an alternative name for the animal in its white winter coat).
Similarly, the Ermine portrait of Queen Elizabeth the First shows her with her pet ferret, which has been decorated with painted-on heraldic ermine spots.
"The Ferreter's Tapestry" is a 15th-century tapestry from Burgundy, France, now part of the Burrell Collection housed in the Glasgow Museum and Art Galleries.
It shows a group of peasants hunting rabbits with nets and white ferrets.
This image was reproduced in "Renaissance Dress In Italy 1400–1500", by Jacqueline Herald, Bell & HymanISBN 0-391-02362-4.
"Gaston Phoebus' Book Of The Hunt" was written in approximately 1389 to explain how to hunt different kinds of animals, including how to use ferrets to hunt rabbits.
Illustrations show how multicolored ferrets that were fitted with muzzles were used to chase rabbits out of their warrens and into waiting nets. 
While unproven, Crivelli has long been presumed to be the subject of Leonardo da Vinci's painting "La belle ferronnière", which is displayed in the Louvre.
The rationale for the Crivelli identification has been primarily based on da Vinci's earlier depiction of Cecilia Gallerani, in his painting, "Lady with an Ermine".
Gallerani had been an earlier mistress of Sforza.
In a 2011 exhibition at the National Gallery, London entitled, "Leonardo Da Vinci: Painter at the Court of Milan" (9 November 2011 – 5 February 2012), the gallery listed the painting as a possible portrait of Beatrice d'Este, wife of Ludovico Sforza, rather than his mistress, Crivelli. 
Cecilia Gallerani (1473–1536), born in Siena, Italy, was the favourite and most celebrated of the many mistresses of Ludovico Sforza, known as Lodovico il Moro, Duke of Milan.
She is best known as the subject of Leonardo da Vinci's painting "The Lady with an Ermine" ("circa" 1489).
While posing for the painting, she invited Leonardo, who at the time was working as court artist for Sforza, to meetings at which Milanese intellectuals discussed philosophy and other subjects.
Cecilia herself presided over these discussions. 
Poland offers a wide spectrum of cultural experience.
Those interested in high culture will enjoy the renowned music festivals like Wratislavia Cantans and the Warsaw Autumn.
Polish museums exhibit remarkable art collections - masterpieces including Leonardo da Vinci's Lady with an Ermine at the Czartoryski Museum in Kraków; the Veit Stoss High Altar in St. Mary's Basilica, Kraków; and the Last Judgement by Hans Memling (The National Museum in Gdańsk).
Ethnographic museums and open-air sightseeing museums also hold attractive collections.
The panorama of Polish culture is completed by a medley of local festivals 
Portrait of a Young Man is a painting in oil on panel, probably from 1513–1514, by the Italian High Renaissance Old Master painter and architect Raffaello Sanzio da Urbino better known simply as Raphael.
The painting was stolen by the Nazis from Poland.
Many historians regard it as the most important painting missing since World War II.
The subject's identity is unverified, but many scholars have traditionally regarded it as Raphael's self-portrait.
The facial features are perceived by specialists as compatible with, if not clearly identical to, the only undoubted self-portrait by Raphael in his fresco "The School of Athens" at the Vatican, identified as such by Vasari.
If it is a self-portrait, no hint is given of Raphael's profession; the portrait shows a richly-dressed and "confidently-poised" young man.
The painting was brought to Poland, along with Leonardo da Vinci's "Lady with an Ermine" and many Roman antiquities, by Prince Adam Jerzy Czartoryski, son of Princess Izabela Czartoryska, on his travels to Italy in 1798.