I came upon this academic resource the other day, a comprehensive French guide to compensating economic damages:
https://www.cours-appel.justice.fr/paris/la-reparation-du-prejudice-economiqueAlthough it is in French, and directly derived from French law, it is nonetheless based on legal and accounting principles which mostly transcend boundaries. Although unlikely to be helpful as a direct reference for most due to its legal and linguistic origins, it is well written, freely available, with clear examples, and can easily be translated using translation tools. I would be interested to see whether others might find it useful to rely upon, even if only to clarify their own thoughts or written arguments when it comes to evaluating damages.
Please don't hesitate to let me know if you find it interesting, or if you have comments or criticisms about it!