Bull, W. A. (2016). Optional instruments of European Union: A definitional, normative and explanatory study (1a. ed.). Intersentia Ltd.
Chicago-viite (17. p.)Bull, William A. Optional Instruments of European Union: A Definitional, Normative and Explanatory Study. 1a. ed. Cambridge: Intersentia Ltd, 2016.
MLA-viite (9. p.)Bull, William A. Optional Instruments of European Union: A Definitional, Normative and Explanatory Study. 1a. ed. Intersentia Ltd, 2016.
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