Willigen, Niels van (2013), Peacebuilding and International Administration: The Cases of Bosnia and Herzegovina and Kosovo, Routledge, pp. 16–, ISBN978-1-134-11718-5: "Crawford (2006) distinguishes three different types of protectorates: protected states, international protectorates, and colonial protectorates. First, protected states are entities which still have substantial authority in their internal affairs, retain some control over their foreign policy, and establish their relation to the protecting state on a treaty or another legal instrument. Protected states still have qualifications of statehood."
Bedjaoui, Mohammed (1991), International Law: Achievements and Prospects, Martinus Nijhoff Publishers, pp. 51–, ISBN92-3-102716-6: "The Treaty of Friendship of 8 August 1949 between Bhutan and India is an example of the creation of a protected State, Bhutan, with a quite loose relationship to the protecting State, India. By the terms of this Treaty of Friendship, Bhutan agreed to follow the guidance given by India in so far as external relations were concerned. India was not granted the power to exercise diplomatic rights on behalf of Bhutan and this way Bhutan remained in charge of its foreign policy."