Effect of seven or three weeks altitude training during a five month training period on hemoglobin mass and performance in national team cross country skiers - Wehrlin, J. P.; Hallen, J.; Clenin, G.; Villiger, B.; Marti, B. (12th Annual Congress of the European College of Sport Science, Jyväskylä, Finland - July 11-14th 2007, 2007)