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Airborne pollen concentration in Leiden, the Netherlands, 1977–1981 ; I. Trees and shrubs flowering in the spring
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Airborne Pollen Concentrations in Leiden, The Netherlands, 1977–1981 ; III. Herbs and Weeds Flowering in the Summer
Proceedings of the 4th International Conference on Mathematics in Sport: MathSport International 2013 Leuven, Belgium 5-7 June 2013