Further study was delayed by European wars.
Still, the authors cautioned that further study was needed.
On the federal level, he said, further study was needed before a judgment could be made.
Further study was hindered, however, by the lack of available texts.
Ms Sibelius cast the issue as one of safety, arguing that further study was needed.
Dr. Bulow called Dr. Crawford's proposal "potentially a significant step forward" but said further study was needed to see how well it might work.
(Reacting to the Michigan study on Tuesday, both a league spokesman and a co-chairman of the league's concussion committee said the study was flawed and further study was necessary).
Bob Colgate, the assistant director of the National Federation of State High School Associations, said the issue of obesity in football was being considered but that further study was needed before any recommendations could be made.
But John A. McGuinn, the chief negotiator for the advertising industry, said the unions should police their own contracts and advertising on the Internet was so new that further study was needed to determine how to pay actors for it.
An active proponent of changes in the military justice system in capital cases, Dwight Sullivan, who was a Marine Corps lawyer from 1987 to 1997, said further study was not needed or warranted.
Dr. Collins said further study was needed, as the available scientific evidence was not clear enough on how much space chimps needed.
