International Conference on Coal Science University of Newcastle-upon-Tyne & IEA Coal Research. (1991). 1991 International Conference on Coal Science proceedings: Proceedings of the International Conference on Coal Science, 16-20 September 1991, University of Newcastle-upon-Tyne, United Kingdom. Butterworth-Heinemann. https://doi.org/10.1016/C2013-0-04522-7
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)International Conference on Coal Science University of Newcastle-upon-Tyne و IEA Coal Research. 1991 International Conference on Coal Science Proceedings: Proceedings of the International Conference on Coal Science, 16-20 September 1991, University of Newcastle-upon-Tyne, United Kingdom. Oxford: Butterworth-Heinemann, 1991. https://doi.org/10.1016/C2013-0-04522-7.
توثيق جمعية اللغة المعاصرة MLA (الإصدار التاسع)International Conference on Coal Science University of Newcastle-upon-Tyne و IEA Coal Research. 1991 International Conference on Coal Science Proceedings: Proceedings of the International Conference on Coal Science, 16-20 September 1991, University of Newcastle-upon-Tyne, United Kingdom. Butterworth-Heinemann, 1991. https://doi.org/10.1016/C2013-0-04522-7.