A journal accepted a paper and then discovered that a very similar paper by the same authors had been published in another journal the previous year. The latter journal carried the piece as a short report while the former planned to publish it as a full paper.
The full paper carries extended research on oral and maxillofacial surgeons while the short report looks only at attitudes of dentists to the treatment of a particular condition. The sample size, methods and results for dentists are identical in each paper, although the emphasis in the two discussions is slightly different. Both papers have been carefully worded to avoid any wholesale duplication of text.
The short report was not mentioned in the reference list of the full paper.