Three people who bought Greg Mortenson's books are taking their claims of fraud against the humanitarian to a federal appeals court.

Last month, U.S. District Judge Sam Haddon dismissed their lawsuit that alleged that Mortenson, his publisher, his co-author and his charity lied in his books "Three Cups of Tea" and "Stones Into Schools" to boost sales and donations.

Haddon called the case flimsy and "fraught with shortcomings."

On Wednesday, attorneys for the readers from Montana and California filed a notice of appeal with the 9th U.S. Circuit Court of Appeals. A fourth plaintiff from Illinois has dropped out of the lawsuit.

The best-selling memoirs recount how Mortenson started building schools in Pakistan and Afghanistan. The lawsuit was filed last year after media reports that Mortenson fabricated parts of them.