Hartwig, Matthias (12 May 2014). "Colour books". In Bernhardt, Rudolf; Bindschedler, Rudolf; Max Planck Institute for Comparative Public Law and International Law (eds.). Encyclopedia of Public International Law. Vol. 9 International Relations and Legal Cooperation in General Diplomacy and Consular Relations. Amsterdam: North-Holland. ISBN978-1-4832-5699-3. OCLC769268852。
Hartwig, Matthias (12 May 2014). "Colour books". In Bernhardt, Rudolf; Bindschedler, Rudolf; Max Planck Institute for Comparative Public Law and International Law (eds.). Encyclopedia of Public International Law. Vol. 9 International Relations and Legal Cooperation in General Diplomacy and Consular Relations. Amsterdam: North-Holland. ISBN978-1-4832-5699-3. OCLC769268852。