Alvaro A. A. Fernandes Andrew Dinn Norman W. Paton M. Howard Williams Olive Liew Extending a deductive object-oriented database system with spatial data handling facilities. 483-497 1999 41 Information & Software Technology 8 http://dx.doi.org/10.1016/S0950-5849(98)00121-9 db/journals/infsof/infsof41.html#FernandesDPWL99