From time to time, BBRC has re-reviewed records that it previously accepted, to ensure they are acceptable in the light of improved knowledge of the species in question. These reviews are carried out on a species-by-species basis. Old World warblers have proved particularly in need of re-review. A review of greenish warbler records was initiated in 1983. The purpose of this review was to establish whether records, particular those in late autumn and winter, of drab grey "Phylloscopus" warblers, which had previously been accepted as greenish warbler, were in fact this species, or were common chiffchaffs of the Siberian race "tristis". 48 records between 1958 and 1970 were examined. Of these, 20 were rejected. A review of Arctic warbler records was begun in 1991, with the aim of determining whether any greenish warblers had been mistakenly accepted as Arctics. The review was completed in 1994, although as of 2009, the results had not been published.