Malte Hübner Serge Autexier Christoph Benzmüller Andreas Meier Interactive Theorem Proving with Tasks. 161-181 2004 103 Electr. Notes Theor. Comput. Sci. http://dx.doi.org/10.1016/j.entcs.2004.02.021 db/journals/entcs/entcs103.html#HubnerABM04