Tusks and Tortoiseshell : the early development of the British plastics industry with special reference to the British Xylonite Company Ltd., 1877-1920 / Peter C. Ashlee. 1982. [iv, 122, ts. Thesis (B.A.) - University of Nottingham, 1982. [Company records of BXL Plastics Ltd.] Tusks and Tortoiseshell: the early development of the British plastics industry