‘Tom Sharkey – Mankiller’ was an article Howard wrote that is now lost. It is not known where Howard submitted it, but it was probably in 1925. 

Howard wrote a letter (#042) to The Ring, circa early 1926 where he mentions Tom Sharkey:

Here is my opinion on the greatest heavyweights of all time:
Boxing reached its height between 1892 and 1905. That was the ring’s Golden Era. The culmination of perfection, the pinnacle of achievement, the greatest heavyweight of all time was James J. Jefferies. Records prove that. During his reign there flourished the greatest collection of heavyweights ever seen, and he was the greatest of all. He defeated all manner of boxers.
In Corbett he beat the fastest heavyweight and the cleverest boxer that ever lived; in Fitzsimmons the most effective hitter of any time; in Tom Sharkey, the greatest of all near champions. While Jefferies would not rank first in skill, speed or hitting ability, for all around prowess he was invincible.
Peter Jackson never saw the day that he could have beaten Jefferies; and the idea of Johnson beating Jefferies when the white man was at his best is ridiculous. Johnson lacked both the ability and the nerve. As for Sullivan and Dempsey, they would have fought themselves out punching Jefferies, and then have been defeated. If there ever was a man who might have won from Jefferies it was Corbett, when at his prime.
This is my rating of heavyweights: James J. Jefferies; James J. Corbett; Jack Dempsey; Peter Jackson; Bob Fitzsimmons; John L. Sullivan; Tom Sharkey; Kid McCoy; Sam Langford; Jack Johnson; Louis Firpo and Jess Willard.

The title and information are gathered from a letter Howard wrote to his friend Tevis Clyde Smith circa February 1929 (letter #101).