@article{Gompertz2009,
  author    = {Benjamin Gompertz},
  title     = {On the nature of the function expressive of the law of human mortality, and on a new mode of determining the value of life contingencies : in a letter to Francis Baily, Esq. F. R. S. \&c.},
  journal   = {Philosophical transactions of the Royal Society of London},
  volume    = {115},
  pages     = {513 -- 585},
  year      = {2009},
}