hoyle's theory was expanded to other processes, beginning with the publication of a review paper in 1957 by burbidge, burbidge, fowler and hoyle (commonly referred to as the bfh paper). this review paper collected and refined earlier research into a heavily cited picture that gave promise of accounting for the observed relative abundances of the elements; but it did not itself enlarge hoyle's 1954 picture for the origin of primary nuclei as much as many assumed, except in the understanding of nucleosynthesis of those elements heavier than iron by neutron capture. significant improvements were made by alastair g. w. cameron and by donald d. clayton. cameron presented his own independent approach (following hoyle's approach for the most part) of nucleosynthesis. he introduced computers into time-dependent calculations of evolution of nuclear systems. clayton calculated the first time-dependent models of the "s"-process and of the "r"-process, as well as of the burning of silicon into the abundant alpha-particle nuclei and iron-group elements, and discovered radiogenic chronologies for determining the age of the elements. the entire research field expanded rapidly in the 1970s.