All contributors who do not meet the criteria for authorship should be listed in the acknowledgments section. Examples of those who might be acknowledged include a person who provided purely technical help, statistical analysis, writing assistance, or a department chair who provided only general support. Authors should disclose whether they had writing assistance and identify the entity that paid for this assistance. Financial and material support should also be acknowledged. Groups of persons who have contributed materially to the paper but whose contributions do not justify authorship may be listed under a heading such as “clinical investigators” or “participating investigators,” and their function or contribution should be described—for example, “served as scientific advisors,” “critically reviewed the study proposal,” “collected data,” or “provided and cared for study patients.” Because readers may infer their endorsement of the data and conclusions, all persons so named must give written permission to be acknowledged.