London, Nov. 25 -- The University of Cambridge's library on Tuesday launched a public appeal to help locate two notebooks of the iconic naturalist and alumnus, Charles Darwin, one of which contains his landmark 1837 Tree of Life sketch, missing since 2001.

Following an exhaustive search, the library curators concluded that the priceless notebooks, first listed as missing in January 2001, have likely been stolen, the university said in the appeal on its website.

The local police have been informed and the missing notebooks added to Interpol's database of stolen artworks.

The appeal launch on November 24 coincides with what is commonly known each year as Evolution Day - recognising the anniversary of Darwin's publication of On the Origin o...