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