https://en.wikipedia.org/wiki/Property_Specification_Language
https://www.doulos.com/knowhow/psl/simple_properties/
https://lsm.epfl.ch/files/content/sites/lsm/files/shared/Reports/stanic_report_2007.pdf
http://simhard.com/wiki/index.php/PSL/The_designers_guide_to_VHDL/18.3_Embedded_PSL_in_VHDL/en
http://www.cse.chalmers.se/edu/year/2009/course/TDA956/Slides/MB_20090326.pdf