Maurice Sendak was the author of the beloved children's books "Where the Wild Things Are," "In the Night Kitchen," "Chicken Soup with Rice" and many more. The author and illustrator, who could be delightfully gruff (see his not-safe-for-work interview with Stephen Colbert), passed away in 2012 at age 84.

In his will, he directed his rare book collection and items of his personal work be gifted to the Rosenbach Museum and Library in Philadelphia, and they haven't been, according to a lawsuit filed by the museum last week.

The Philadelphia Inquirer reports that Sendak's relationship with the museum dates to the 1960s, when he began placing his work there on deposit. He was at times a board member and its honorary president. The museum presented dozens of shows of his work.