Instruction: Parse the product information to locate the target attribute, and then provide the extracted value of the target attribute and its source in the output, specifying None if the attribute is not present.

Input:
Product title: The Legend of Caleb York (A Caleb York Western)
Product description: Mickey Spillane is the legendary crime writer credited with igniting the explosion of paperback publishing after World War II through the unprecedented success of his Mike Hammer novels. Spillane's novels sold tens of millions of copies. I, The Jury went through more than 60 paperback printings in 1947 alone. In 1995, he was named a Grand Master by the Mystery Writers of America. Before his death at the age of 88 in 2006, Spillane chose long-time friend Max Allan Collins to complete his unfinished works and act as his literary executor. Max Allan Collins is the New York Times bestselling, award-winning author of Road to Perdition , the graphic novel that inspired the Oscar-winning movie starring Paul Newman and Tom Hanks. Also a filmmaker, Collins created the documentary Mike Hammer's Mickey Spillane . He lives in Iowa. For more information about the Caleb York westerns by Mickey Spillane and Max Allan Collins, visit www.maxallancollins.com.
Product brand: Mickey Spillane
Target attributes: Format
Answer: attribute: format
value: paperback
source: product description