Petrova, Jordanka; Momchilova, Snejana; Vassilev, Nikolay G., Phosphorus, Sulfur and Silicon and the Related Elements, 1992, vol. 68, # 1-4, p. 45 - 52
Petrova, Jordanka; Momchilova, Snejana; Vassilev, Nikolay G., Phosphorus, Sulfur and Silicon and the Related Elements, 1992, vol. 68, # 1-4, p. 45 - 52