Great Britain & Great Britain. Foreign and Commonwealth Office. (1980). Agreement between the government of the United Kingdom of Great Britain and Northern Ireland and the government of the Democratic Socialist Republic of Sri Lanka for the promotion and protection of investments: Colombo, 13 February 1980 (instruments of ratification have not been exchanged). H.M.S.O..
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Great Britain و Great Britain. Foreign and Commonwealth Office. Agreement Between the Government of the United Kingdom of Great Britain and Northern Ireland and the Government of the Democratic Socialist Republic of Sri Lanka for the Promotion and Protection of Investments: Colombo, 13 February 1980 (instruments of Ratification Have Not Been Exchanged). London: H.M.S.O., 1980.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Great Britain و Great Britain. Foreign and Commonwealth Office. Agreement Between the Government of the United Kingdom of Great Britain and Northern Ireland and the Government of the Democratic Socialist Republic of Sri Lanka for the Promotion and Protection of Investments: Colombo, 13 February 1980 (instruments of Ratification Have Not Been Exchanged). H.M.S.O., 1980.