ISBN 978-0-8493-0982-3* Gawthrop, P. J. and Ballance, D. J., 1999: "Symbolic computation for manipulation of hierarchical bond graphs" in "Symbolic Methods in Control System Analysis and Design", N. Munro (ed), IEE, London, ISBN 0-85296-943-0.
ISBN 978-0-8493-0982-3* Gawthrop, P. J. and Ballance, D. J., 1999: "Symbolic computation for manipulation of hierarchical bond graphs" in "Symbolic Methods in Control System Analysis and Design", N. Munro (ed), IEE, London, ISBN 0-85296-943-0.