He [Van] was out, he imagined, na progulke (promenading) in the gloomy firwood with Aksakov, his tutor, and Bagrov's grandson, a neighbor's boy, whom he teased and pinched and made horrible fun of, a nice quiet little fellow who quietly massacred moles and anything else with fur on, probably pathological. (1.24)

Darkbloom ('Notes to Ada'): allusion to Childhood Years of Bagrov's Grandson by the minor writer Sergey Aksakov (A. D. 1791-1859).

On the other hand, Bagrov's grandson brings to mind Bogrov, a police agent who in September, 1911, assassinated Stolypin (the Russian Premier Minister) in Kiev's opera theatre. Like Stolypin, Abraham Lincoln (1809-65, the 16th President of the USA) was assassinated in a theatre. At Van's first tea party in Ardis Marina mentions Lincoln's second wife:

'I used to love history,' said Marina, 'I loved to identify myself with famous women. There's a ladybird on your plate, Ivan. Especially with famous beauties - Lincoln's second wife or Queen Josephine.' (1.5)

It is John Milton (1608-74), the author of Paradise Lost (1667) and Paradise Regained (1671), who was married twice and who wrote on divorce (Doctrine and Discipline of Divorce, etc.). On Antiterra (Eath's twin planet also known as Demonia) Milton is blended with Lincoln (who had one wife):

But (even more absurdly), if, in Terrestrial spatial terms, the Amerussia of Abraham Milton was split into its components, with tangible water and ice separating the political, rather than poetical, notions of 'America' and 'Russia,' a more complicated and even more preposterous discrepancy arose in regard to time - not only because the history of each part of the amalgam did not quite match the history of each counterpart in its discrete condition, but because a gap of up to a hundred years one way or another existed between the two earths; a gap marked by a bizarre confusion of directional signs at the crossroads of passing time with not all the no-longers of one world corresponding to the not-yets of the other. (1.3)

In her erratic student years Aqua had left fashionable Brown Hill College, founded by one of her less reputable ancestors, to participate (as was also fashionable) in some Social Improvement project or another in the Severnïya Territorii. She organized with Milton Abraham's invaluable help a Phree Pharmacy in Belokonsk, and fell grievously in love there with a married man, who after one summer of parvenu passion dispensed to her in his Camping Ford garçonnière preferred to give her up rather than run the risk of endangering his social situation in a philistine town where businessmen played 'golf' on Sundays and belonged to 'lodges.' (ibid.)

Abraham Lincoln was assassinated by an actor. In Shakespeare's Hamlet (1601) Hamlet asks Polonius to use the actors "after your own honour and dignity - the less they deserve the more merit is in your bounty" (Act Two, scene 2):

"God's bodkin, man, much better! use every man after his desert, and who shall 'scape whipping?" (Hamlet's words are quoted by Fomin in Aldanov's Klyuch, "The Key," Part Two, Chapter II).

In his famous monologue (3.1) Hamlet mentions "a bare bodkin:"

For who would bear the Whips and Scorns of time,
The Oppressor's wrong, the proud man's Contumely,
The pangs of despised Love, the Law’s delay,
The insolence of Office, and the Spurns
That patient merit of the unworthy takes,
When he himself might his Quietus make
With a bare Bodkin?

Quietus is the name of the pills that the Robinsons (an elderly couple onboard Admiral Tobakoff) give Lucette:

No wonder the place [Tobakoff's cinema hall] was emptovato, as Lucette observed, and she went on to say that the Robinsons had saved her life by giving her on the eve a tubeful of Quietus Pills. (3.5)

Lucette to Van: 'You'll have them with Miss Condor' (nasalizing the first syllable) 'when I go to dress. For the moment I want only tea. Mustn't mix drugs and drinks. Have to take the famous Robinson pill sometime tonight. Sometime tonight.' (ibid.)

"The Condor" and My vse - Robinzony ("We all Robinson Crusoes") are the poems by Bryusov. Bryusov is the author of several poems on Lenin's death (one of them was meant as the new words of Mozart's Requiem). In Aldanov's Begstvo ("The Escape," 1932) Fedosiev and Braun work out the plan of Lenin's assassination.

Bodkin ("a Danish stilletto") brings to mind Kinbote, the name assumed by Charles Xavier Vseslav, the self-exiled last king of Zembla who is assassinated by Jakob Gradus in VN's Pale Fire (1962). 'Pale Fire with Tom Cox Up' is a steeplechase picture that hangs above Cordula's and Tobak's bed in their Tobakoff cabin:

There hung, she said, a steeplechase picture of 'Pale Fire with Tom Cox Up' above dear Cordula's and Tobak's bed, in the suite 'wangled in one minute flat' from them, and she wondered how it affected the Tobaks' love life during sea voyages. (ibid.)

Admiral Tobakoff is Van's favorite liner (3.3), but sometimes he travels onboard Queen Josephine.

In a letter of March 30, 1895, to Suvorin Chekhov says that Yavorski is a daughter of Kiev's chief of police Huebenneth. According to Chekhov, she has in her arteries the blood of an actress and in her veins the police blood:

Побывайте на Madame Sanse Gêne и посмотрите Яворскую. Если хотите, познакомьтесь. Она интеллигентна и порядочно одевается, иногда бывает умна. Это дочь киевского полицеймейстера Гюбеннета, так что в артериях её течёт кровь актёрская, а в венах полицейская. О преемственности сих двух кровей я уже имел удовольствие высказывать Вам свое психиатрическое мнение. Московские газетчики всю зиму травили её, как зайца, но она не заслуживает этого. Если бы не крикливость и не некоторая манерность (кривлянье тож), то это была бы настоящая актриса.

Chekhov recommends to Suvorin Yavorski in the part of Madame Sanse Gêne (the title character of a play by Sardou and Moreau). Sardou brings to mind "Mr and Mrs Sardi" mentioned by Van:

They could have eloped to Lopadusa as Mr and Mrs Sardi or Dairs! (3.5).

Sardi and Dairs are anagrams of Ardis. Describing the family dinner in "Ardis the Second," Van mentions Ada's sisterly sanse gêne:

At this moment both battants of the door were flung open by Bouteillan in the grand manner, and Demon offered kalachikom (in the form of a Russian crescent loaf) his arm to Marina. Van, who in his father's presence was prone to lapse into a rather dismal sort of playfulness, proposed taking Ada in, but she slapped his wrist away with a sisterly sans-gêne, of which Fanny Price might not have approved. (1.38)

In a letter of June 12, 1891, to Lika Mizinov Chekhov wrote:

We have a magnificent garden, dark avenues, snug corners, a river, a mill, a boat, moonlight, nightingales, turkeys. In the pond and river there are very intelligent frogs. We often go for walks, during which I usually close my eyes and crook my right arm in the shape of a bread-ring [krendelem], imagining that you are walking by my side.

Instead of signature Chekhov drew an arrow-pierced heart.

The hero and narrator of Chekhov's Rasskaz neizvestnogo cheloveka ("The Story of an Unknown Man," 1895) is a reformed terrorist who planned the assassination of a high official.

p. s. to my previous post: the Braille Club in Raduga is mentioned in the library chapter of Ada (1.21).