Akio Fujiyoshi Masakazu Suzuki Seiichi Uchida Verification of Mathematical Formulae Based on a Combination of Context-Free Grammar and Tree Grammar. 415-429 2008 AISC/MKM/Calculemus http://dx.doi.org/10.1007/978-3-540-85110-3_35 conf/aisc/2008 db/conf/aisc/aisc2008.html#FujiyoshiSU08