There are some links, that I am afraid don't work:
17.14.1 Packages that Org cooperates with ‘calc.el’ by Dave Gillespie [...] See Section “Embedded Mode” in calc. # that link doesn't work, it seems it tries to open the file calc.pdf‘constants.el’ by Carsten Dominik [...] http://www.astro.uva.nl/~dominik/Tools.
# That link is dead. Maybe this would be the correct one: https://staff.fnwi.uva.nl/c.dominik/#orgf869524
Best regards