Please read Alexey Sklyarenko's annotations on Pale Fire, Ada and other Nabokov works here.
Before the family dinner in "Ardis the Second" Van Veen (the narrator and main character in VN’s novel Ada, 1969) asks his father where did he get his tan:
Demon shed his monocle and wiped his eyes with the modish lace-frilled handkerchief that lodged in the heart pocket of his dinner jacket. His tear glands were facile in action when no real sorrow made him control himself.
When Ada refuses to leave her sick husband, Andrey Vinelander, Van Veen (the narrator and main character in VN’s novel Ada, 1969) calls her "Helen of Troy, Ada of Ardis:"
As had been peculiar to his nature even in the days of his youth, Van was apt to relieve a passion of anger and disappointment by means of bombastic and arcane utterances which hurt like a jagged fingernail caught in satin, the lining of Hell.
Describing the forty days after Queen Blenda’s death, 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) mentions a volume of Historia Zemblica and the picture of a bogtur (ancient warrior) in the histo
Describing the torments of poor mad Aqua (the twin sister of Marina, Van’s, Ada’s and Lucette’s mother), Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions Altar and Palermontovia:
The narrator and main character in VN's novel Ada (1969), Van Veen calls his and Ada's ear-trumpet age our "dot-dot-dotage:"
Before the family dinner in "Ardis the Second" Demon Veen (in VN's novel Ada, 1969) recollects a batch of old, orange-juice-stained Povesa (playboy) magazines that he saw in Akapulkovo (a Mexican resort whose name blends Acapulco with Pulkovo, the site of an observatory and airport near St. Petersburg):
Demon shed his monocle and wiped his eyes with the modish lace-frilled handkerchief that lodged in the heart pocket of his dinner jacket. His tear glands were facile in action when no real sorrow made him control himself.
Describing the torments of poor mad Aqua (the twin sister of Van's, Ada's and Lucette's mother Marina), Van Veen (the narrator and main character in VN's novel Ada, 1969) mentions stone-heavy-dead St Zeus whom they carried through the gradual, gradual shade:
Describing the beginning of his life-long romance with Ada, Van Veen (the narrator and main character in VN's novel Ada, 1969) mentions his diary, a shagreen-bound book:
Offering Ada a ride in the park, Van Veen (the narrator and main character in VN’s novel Ada, 1969) mentions two horses, Pardus and Peg:
‘Now let’s go out for a breath of crisp air,’ suggested Van. ‘I’ll order Pardus and Peg to be saddled.’
Describing Lucette's visit to Kingston (Van's American University), Van Veen (the narrator and main character in VN's novel Ada, 1969) mentions old Rattner, resident pessimist of genius: