The Year-Books contain cases in chronological order from 1268-1535. The court sessions were divided into four terms: Hilary (early January—early April); Easter (Pasche) (mid-April—May); Trinity (June—July); and Michaelmas (October—December). The Year-Books first appeared in manuscript on parchment and were stored in rolls (rotuli). References to cases even long after the advent of printing might appear as T.19.H.8.rot 330 (Trinity term, nineteenth year of the reign of Henry VIII (1527), roll 330) -- as shown.
With the advent of printing, references to a year-Book took the form P.40.E.3 -- Easter term (Pasche), fortieth year of the reign of Edward III (1366). This left a legal researcher with an entire term to search for a single case. Tottel's first attempt at greater precision was numbering of the cases (placita) in each term -- which produced citations such as P.40.E.3.pl.28. This is the reference to the case in the Year-Book pictured below -- the year and the monarch are noted in the header, the placita number, 28, is in the right-hand margin. The image at right shows a citation to Hilary term, fourteenth year of the reign of Henry VIII (1524), placita 6, with the additional note that the case falls on folio 17. Tottell further refined his system by providing regular foliation, or numbering leaves in a book, permitting citations such as P.40.E.3.25 -- the folio shown below. By enforcing rigid foliation of his editions, Tottell was able to cite not only to the quarter of a particular year and the case number, but the folio on which a particular issue was discussed. The foliation began at 1 each year.
His method was so useful that it became widely adopted, both by other printers and by practitioners -- as the marginal notes above demonstrate.
For more about Year-Books, see the page on Tottell's Year-Book of Edward III.