This was the period when the ballad emerged as a significant written form in Scotland. Some ballads may date back to the late medieval era and deal with events and people that can be traced back as far as the thirteenth century, including "Sir Patrick Spens" and "Thomas the Rhymer", but which are not known to have existed until the eighteenth century. They were probably composed and transmitted orally and only began to be written down and printed, often as broadsides and as part of chapbooks, later being recorded and noted in books by collectors including Robert Burns and Walter Scott. From the seventeenth century they were used as a literary form by aristocratic authors including Robert Sempill (c. 1595–c. 1665), Lady Elizabeth Wardlaw (1627–1727) and Lady Grizel Baillie (1645–1746).