a J Walker, A. Acock, S. Bowman, и F. Li. The journals of gerontology. Series B, Psychological sciences and
social sciences, 51 (3):
P130--42(мая 1996)
R. Jahns, V. Boivin, C. Siegmund, G. Inselmann, M. Lohse, и F. Boege. Circulation, 99 (5):
649-54(февраля 1999)Jahns, R Boivin, V Siegmund, C Inselmann, G Lohse, M J Boege, F Research
Support, Non-U.S. Gov't United states Circulation Circulation. 1999
Feb 9;99(5):649-54..