 Wyclif produced a very large body of work, both in Latin and English, a great portion of which has been edited by the Wyclif Society between the end of the 19th and the beginning of the 20th centuries, even though some of his most important books are still unpublished — for instance, his treatises on time (De tempore) and on divine ideas (De ideis). W. R. Thomson 1983 wrote a full bibliography of Wyclif’s Latin writings, among which the following can be mentioned: De logica (On Logic — ca. 1360); Continuatio logicae (Continuation of [the Treatise on] Logic — date of composition: about 1360–63 according to Thomson 1983, but between 1371 and 1374 according to Mueller 1985); De ente in communi (On Universal Being — ca. 1365); De ente primo in communi (On Primary Being — ca. 1365); De actibus animae (On the Acts of Soul – ca. 1365); Purgans errores circa universalia in communi (Amending Errors about Universals — between 1366 and 1368); De ente praedicamentali (On Categorial Being — ca. 1369); De intelleccione Dei (On the Intellection of God – ca. 1370); De volucione Dei (On the Volition of God – ca. 1370); Tractatus de universalibus (Treatise on Universals — ca. 1368–69 according to Thomson 1983, but between 1373 and 1374 according to Mueller 1985); De materia et forma (On matter and form — between late 1370 and early 1372 according to Thomson 1983, but about 1374–75 according to Mueller 1985). Many of these treatises were later arranged as a Summa, called Summa de ente (Summa on Being), in two books, containing seven and six treatises respectively. (On the genesis, nature, structure, and tasks of this work see Robson 1961, pp. 115–40.)