For as much as Lee Berthelsen knows about the career of his Impressionist painter father, the sheer output of his work remains a guess. "We have never been able to come up with a number, but I can tell you it's somewhere between 5,000 and 12,000 paintings," Lee said. Johann Berthelsen's favorite subject was New York in the snow, with skyline scenes of concrete and steel softened by gently falling flakes. And among his many famous buyers was Frank Sinatra, who once paid Johann to paint a portrait of Ava Gardner's dog. After Gardner died in 1990, auctioneers of her estate tried to claim Sinatra himself had captured the dog on canvas, but Lee knew better and authenticated it as his father's work. ....the Johann Berthelsen Conservancy in Milwaukee... the website says it's devoted to tracking, assembling and promoting Johann's artworks, sharing his story and providing authentication to root out copies and counterfeits. His New York scenes in particular are, in Lee's words, "wonderfully sellable and very collectible," and some have sold at auction for more than $50,000. In the 1980s, a museum in Indianapolis organized a show of Berthelsen works, and Lee determined that nearly all of the 55 paintings were fakes. "My dad has been forged. It's mind-boggling to me. I have personally come across the last 35 years maybe a little under 500 forgeries," he said. ....Dag Hammarskjold was secretary-general of the United Nations when he commissioned Johann to paint an image of the U.N. building in New York. He wanted it to exude peacefulness. "It's a reminder that if I do my job, I will help bring tranquillity to the world," he told the artist. (http://archive.jsonline.com/news/milwaukee/son-strives-to-preserve-johann-berthelsens-impressionist-paintings-b99398685z1-284222911.html)