CUSHING, ME (AP).- Andrew Wyeth’s famous painting “Christina’s World” shows a crippled woman dragging herself across a field toward a farmhouse. A tour of the house, which was declared a National Historic Landmark June 30, offers a fascinating, in-depth look at the real world of Christina Olson and her family, and also reveals the story of Wyeth’s relationship with them. Wyeth spent 30 years producing some 300 works of art depicting the Olsons and their home in Cushing, Maine. This summer and fall offer a rare opportunity to see 50 of those paintings and drawings at the Farnsworth Art Museum‘s Wyeth Center in the nearby town of Rockland, where they are on loan from Marunuma Art Park in Asaka, Japan, through Oct. 30, in a show called “Andrew Wyeth, Christina’s World and the Olson