<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/digimathbycategory.html].</ref>
</references>
[http://www.ucalgary.ca/aslcle/logic-courseware/].
[http://www.cs.ru.nl/freek/digimathbycategory.html]