 The various cadastral units appear on certificates of title, which are given volume and folio numbers; these numbers by themselves are sometimes used to identify land parcels, or in combination with the other units.Detailed maps of these divisions have been required since the introduction of the Torrens title system of a central register of land holdings in South Australia in 1858, which spread to the other colonies.While cadastral data since the 1980s has been digitalised, there remain many old maps showing these divisions held in collections of Australian libraries such as the National Library of Australia, as well as in state libraries.