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CHICAGO, IL - MAY 27: Actress, comedian, and writer Joan Rivers attends Michigan Avenue Magazine Celebrates Its Women Of Influence, May/June Issue With Joan Rivers at Neiman Marcus Chicago on May 27, 2014 in Chicago, Illinois. (Photo by Jeff Schear/Getty Images for Michigan Avenue Magazine)

Late popular comedian-actress Joan Rivers’ private letters from stars including Meryl Streep and Tom Hanks will be published in her new biography.

Rivers died in 2014 at the age of 81 after suffering a heart attack during a routine medical procedure.

Though Rivers rarely apologised for her acid tongue, fans will see a softer side to her in new book, Joan Rivers Confidential.

Written by Rivers’ daughter Melissa Rivers and friend-and-publicist Scott Currie, Joan Rivers Confidential will feature private letters belonging to the Fashion Police star, sent by the likes of Meryl Streep.

Streep and other celebrities including Tom Hanks, David Letterman and Bo Derek have given permission for their private letters to Rivers to be published.