The Times (London), December 2, 1867, and again on November 28, 1871, both times in regards to Cato's wins at the Birmingham Dog Show
The Times (London) again for wins at the Grand National Exhibition of Sporting and Other Dogs in London: on June 23, 1870, where Cato took first place in the Newfoundland dog class at the first iteration of this dog show, and again on June 6, 1872, when Cato took first place again.
John Henry Walsh's
The Dogs of the British Islands (1867)
Gordon Stables'
Ladies' Dogs as Companions (1879)
Cato's fame even crossed the pond, for he was mentioned in G. O. Shield's
The American Book of the Dog (1891)
Rawdon Briggs Lee's
A History and Description of the Modern Dogs of Great Britain and Ireland. (Non-sporting division) (1894)
Edwin Noble's
The Dog Lover's Book (1910) singles Cato out for special mention.
Dogdom, September, 1917