 By 1971, when a bibliography of "ab initio" calculations was published, the largest molecules included were naphthalene and azulene.Abstracts of many earlier developments in "ab initio" theory have been published by Schaefer.In 1964, Hückel method calculations (using a simple linear combination of atomic orbitals (LCAO) method to determine electron energies of molecular orbitals of π electrons in conjugated hydrocarbon systems) of molecules, ranging in complexity from butadiene and benzene to ovalene, were generated on computers at Berkeley and Oxford.