Philosophical Transactions of the Royal Society of London. Series A. Mathematical, Physical and Engineering Sciences (Philos. Trans. R. Soc. Lond. Ser. A Math. Phys. Eng. Sci.) (20060101), 364, no.~1844, 1769-1794. ISSN: 1364-503X (print).eISSN: 1471-2962.