References
Nuclear science abstracts, 0029-5612Computer & control abstracts, 0036-8113, 1968-Electrical & electronics abstracts, 0036-8105, 1968-Physics abstracts. Science abstracts. Series A, 0036-8091, 1968-Chemical abstracts, 0009-2258International aerospace abstracts, 0020-5842Mathematical reviews, 0025-5629