Please read Alexey Sklyarenko's annotations on Pale Fire, Ada and other Nabokov works here.
On the day preceding Ada's sixteenth birthday (July 21, 1888) Greg Erminin (in VN's novel Ada, 1969, Grace's twin brother) gives Ada a little camel of yellow ivory carved in Kiev, five centuries ago, in the days of Timur and Nabok:
Describing his novel Letters from Terra, Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions the poet Max Mispel and his article ‘The Weed Exiles the Flower’ (Melville & Marvell):
In VN's novel Otchayanie ("Despair," 1934) Hermann Karlovich (the narrator and main character) says that he likes to bind words by the mock marriage of a pun:
Мне нравилось – и до сих пор нравится – ставить слова в глупое положение, сочетать их шутовской свадьбой каламбура, выворачивать наизнанку, заставать их врасплох. Что делает советский ветер в слове ветеринар? Откуда томат в автомате? Как из зубра сделать арбуз?
In VN’s novel Ada (1969) Van Veen (the narrator and main character) learns card tricks from Mr Plunkett (a reformed card-sharper):
The action in VN's novel Ada (1969) takes place on Demonia, Earth's twin planet also known as Antiterra. In VN's novel Dar ("The Gift," 1937) Fyodor Konstantinovich Godunov-Cherdyntsev (the narrator and main character) describes his first collection of poetry and mentions mir prekrasnykh demonov (a world of handsome demons) that develops side by side with us, in a cheerfully sinister relationship to our everyday existence:
At the end of his short poem “The Nature of Electricity” quoted by Kinbote (Shade’s mad commentator who imagines that he is Charles the Beloved, the last self-exiled king of Zembla) in his Commentary John Shade (the poet in VN's novel Pale Fire, 1962) mentions "the torments of a Tamerlane, the roar of tyrants torn in hell:"
vino + Gradus + Troystvo = vinograd + ustroystvo
vino - Russ., wine
Gradus - Jakob Gradus (one of the three main characters in Pale Fire, Shade's murderer; gradus is Russian for "degree")
Troystvo - "The Threesome," a poem (1830) by Shevyryov
vinograd - Russ., grape; Vinograd ("The Grapes," 1824) is a poem by Pushkin
According to Kinbote (in VN's novel Pale Fire, 1962, Shade’s mad commentator who imagines that he is Charles the Beloved, the last self-exiled king of Zembla), Gradus (Shade's murderer) contended that the real origin of his name should be sought in the Russian word for grape, vinograd, to which a Latin suffix had adhered, making it Vinogradus:
Line 17: And then the gradual; Line 29: gray
In Canto Three of his poem John Shade (the poet in VN's novel Pale Fire, 1962) describes IPH (a lay Institute of Preparation for the Hereafter) and compares tips offered by the Institute to the amber spectacles for life's eclipse:
While snubbing gods, including the big G,
Iph borrowed some peripheral debris
From mystic visions; and it offered tips
(The amber spectacles for life's eclipse) -
How not to panic when you're made a ghost:
Sidle and slide, choose a smooth surd, and coast,
In Canto Three of his poem John Shade (the poet in VN's novel Pale Fire, 1962) describes IPH (a lay Institute of Preparation for the Hereafter):
L'if, lifeless tree! Your great Maybe, Rabelais: