Pale Fire created by Kinbote, features an entry for a "Botkin, V.," describing this Botkin as an "American scholar of Russian descent"—and referring to a note in the Commentary on line 894 of Shade's poem, in which no such person is directly mentioned but a character suggests that "Kinbote" is "a kind of anagram of Botkin or Botkine". In this interpretation, "Gradus" the murderer is an American named Jack Grey who wanted to kill Judge Goldsworth, whose house "Pale Fire's" commentator—whatever his "true" name is—is renting. Goldsworth had condemned Grey to an asylum from which he escaped shortly before mistakenly killing Shade,
Pale crag martin often treated as the small, pale northern subspecies of the rock martin, but it is now usually considered to be a separate species. The changes in size and colour are continuous, so the evidence for separate species is not strong, although some rock martins can weigh more than twice as much as the smallest subspecies of the pale crag martin. The average weight for "P. o. fusciventris" is 22.4 g (0.79 oz) against 10 g (0.35 oz) for "P. o. obsoleta". There do not appear to be any intermediate forms where pale crag martins and rock martin populations breed close