The definition of each word in the OED is based on written evidence of the word in use. A selection of this evidence appears in the Dictionary in the form of a set of short quotations illustrating the definition.
Great care must be taken to ensure that this evidence is reliable. A specialist group of bibliographical editors ensure that the quotations that appear in the Dictionary are cited from the earliest or most reliable editions of works, so that the text and date of evidence are as accurate as possible.
Checking the evidence
The earliest evidence for the word concession cited in the original OED is as follows:
1647 CLARENDON Hist. Reb. (1843) I. 6/1 By his concession of the violent passion his highness was transported with.
This quotation came from the 1843 edition of the Earl of Clarendon’s History of the Rebellion and Civil Wars in England. The reader assumed that the text was the same in the original manuscript of 1647, and the OED gave this as the date of the quotation. On checking, however, the same passage in the first edition (published in 1702) reads ‘By his Yielding …’. The word concession does not appear at all. The OED therefore cannot cite 1647 as the date of the earliest recorded evidence of this word, and the revised quotation reads:
In the First Edition of the OED the same work might be cited in a number of different ways. This did not particularly concern the readers of the 1880s, but nowadays, when an alternative method of accessing the OED is through text searching, it can be problematic if citation styles are not standard. Although there remains some variation in the OED database, the data it contains is much more streamlined than it was even five years ago.