Acta Academiae Aboensis, Series B: Mathematica et Physica, , vol. 12, # 1 p. 3,11 Acta Academiae Aboensis, Series B: Mathematica et Physica, , vol. 12, # 7 p. 3,24 Acta Academiae Aboensis, Series B: Mathematica et Physica, , vol. 14, # 1 p. 3,25, 26, 32, 35