Some Details

Three ship's surgeons, opposite numbers of Dr McCoy:

in "Nor Iron Bars," Dr Hoyle on the Flyaway II to Alpha Centauri;

in "A Dusk of Idols," Dr Rosenbaum on an unnamed ship returning from the Heart stars;

in "And Some Were Savages," Dr Clyde Bixby on the UNSS Brock Chisholm.

Three references to Canes Venatici:

in "This Earth of Hours," the planet Calle orbits a star in the Canes Venatici cluster which, in this context, has to mean a star cluster in the Canes Venatici constellation, not a cluster of galaxies;

in "Beep"/The Quincunx Of Time, the planet Hathshepa orbits a star on the rim of the eleven light year distant galaxy NGC 4725 in the constellation of Canes Venatici;

in "A Style in Treason," there is an Emperor of Canes Venatici.

In its timeline, Calle is an outpost of the Central Empire of the galaxy, thus is not part of any cluster empire such as the one in "A Style in Treason." The galaxy of "A Style in Treason" is rich in empires since the Green Exarch "...drew tithes from six fallen empires older than man..." (Anywhen, New York, 1970, p. 19).