Harlequin Mills and Boon Romance
Before establishing Mills & Boon Australia in 1974, the Mills & Boon Romances were made available in Australia by importing booksellers. After that time the Australian edition, published two month after the UK release, had different covers but kept the Mills & Boon ISBN.
Starting in 1992 the Mills & Boon Romances of Australia had their own numbering and ISBN. The UK line of Mills & Boon Medical Romances were incorporated in the Australian Romance imprint as well as Larger Print editions of earlier titles. In 1994 the imprint was renamed to Harlequin Mills & Boon Romances and in 1998 the line was spilt into Sexy and Sweet Romances but kept the continuous numbering. Starting August 2009, the numbering appears to have been discontinued all together. See listings of titles after July 2009 in seperate listings here Medical, Sexy, and Sweet.