Chaffinch's Mythology Bullfinch's Mythology is a standard book of classical European mythology that.students will run into in courses on the subject
Harper paperback, p37 "Enochi... Athootita... 'Guilt and 'Innocence'" This is in fact Greek, ενοχή & αγνότητα.
Doubleday Hardback, p163 A call-back to Pyramids in a discussion about the intent and purposes of grave-goods.
Doubleday Hardback, PP 170-71 Eumenides Treason decrees she should go into the grave with a ham sandwich to sustain her in the afterlife. There is a dialogue with DEATH on the post-mortem status of sandwich materials and condiments. This could be compared to Sir Terry Pratchett, writing in Book:A Slip of the Keyboard, on his own near-death experience on the operating table where an otherwise routine operation got rather less routine. Terry was witnessed to sit up and have a dialogue with an unseen other party about sandwiches. Ham ones. (pp47-49, in article "A Scribbling Intruder")
Doubleday Hardback, p234 Reading the pulp-fiction romance novel provided by the Feegle, Tiffany realises looking for nuts in June is a euphemism for something else entirely. She translates it into the familiar Chalk euphemism looking for cuckoo nests. Compare this to the old English folk ballad Drink Down The Moon, one of those songs Granny Weatherwax would term "one of them songs, about goings-on" and for which Nanny Ogg would know all the words and verses. Steeleye Span, one of Terry's favourite bands, do a very good version. Listen to it here
Doubleday Hardback, p240 a group of otherwise streetwise Ankh-Morpork kids are talking to what is apparently a sentient snowman. One hopefully asks Is there any chance you can take us flying? But no walking in the air for them.
Harper paperback, p336 "снова похолодало" is Russian for "it got cold again" according to Google Translate
Harper paperback, p379 "Orpheo rescuing Euniphon from the Underworld" Orpheus rescues Eurydice from the Underworld in Greek legend
Harper paperback, p423 "'An' don't look back until we're well oot o' here,' said Rob Anybody. 'It's kind of traditional.'" Orpheus was told not to look back at Eurydice while leaving the Underworld but he did & Eurydice was trapped.