The many different forms of non-standard BBN have been reviewed by Coles & Lucchin [22] and Jedamzik [157]. Much work has been devoted to inhomogeneous baryon distributions during BBN, additional relativistic particles, decaying particles, large neutrino chemical potentials (e.g. [158]), sterile neutrinos (e.g. [159]), magnetic fields (e.g. [160]), anti-matter domains (e.g. [161]), and alternative theories of gravity (e.g. [162]).