1. North Carolina State University; Raleigh, North Carolina U.S.A.
2. Johns Hopkins University; Baltimore, Maryland U.S.A.
3. Maastricht University; Maastricht The Netherlands
4. University of Southern Denmark; Odense Denmark
5. University of Pittsburgh; Pittsburgh, Pennsylvania U.S.A.
6. National Institute on Aging; Bethesda, Maryland U.S.A.