For keycodes which have mathematical significance (i.e. are mathematical expressions and can be calculated directly, with numerical methods or simply can be expressed with mathematical principles) the reference to derivation of the keycode should be include. Simpler models may derived as part of the Data Dictionary reference page but this should only be done in the shortest of derivations.
Full attribution of the derivation is not only a courtesy – it is a ethical requirements and plagiarism is one of the few misdemeanors that will be cause for direct action by the HRI community.