<references>
<ref name=asl>DITMARSCH, H. van. Logic courseware. 2010. A Comprehensive list of Tools for doing Logic. Association for Symbolic Logic. Disponível em: [http://www.ucalgary.ca/aslcle/logic-courseware/]. </ref>
<ref name=wiedijk>WIEDIJK, F. Digital Math by Categories with Samples. 2007. A compiled list of 300 Tools sorted by implementation, interaction, supported logic and size effort. Disponível em: [http://www.cs.ru.nl/~freek/digimathbycategorydigimath/bycategory.html].</ref>
</references>