The 12-book MicropÃ dia is one of the three parts of the 15th edition of EncyclopÃ dia Britannica , and the other two being the one-book PropÃ dia and the 17-book MacropÃ dia . The 12-volume MicropÃ dia is one of the three parts of the 15th edition of EncyclopÃ dia Britannica , the other two being the one-volume PropÃ dia and the 17-volume MacropÃ dia .