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the cell with axial symmetry and different type of obstacles (I), (to
appear).
[2] H. Poincaré, Calcul des Probabilitiés, Ed. 2, Carré, Paris,
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[3] M. Stoka, Probabilitiés géométriques de type Buffon dans le
plan Euclidien, Atti Acc. Sci. Torino T. 110 (1975-1976), 53-59.