Text reuse detection with word shingles (Broder 1997): text and corpus documents...
https://text.halowerk.com/v1/corpus-overlapOverview
Text reuse detection with word shingles (Broder 1997): text and corpus documents are segmented into words (Unicode, NFKC, lower case); every run of n words (default 5) is hashed (32-bit FNV-1a) and compared through a hash index of the text. Matching shingles are chained along diagonals into maximal passages, verified word by word against hash collisions and kept from min_passage_words (default 8) words on; each passage reports start and end offsets in the text and in the document.