Definition: Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.
Input: Abstract: Pillars of calcification are rarely found in the skin. An interesting case is described where rows of new bone developed in the skin which had been grafted 31 years previously to cover partial skin thickness burns of the shin. The problems of heterotropic ossification are discussed.

Time Factors.