@article{gautschi:1959:eil,
    author = {Gautschi, Walter},
     title = {Exponential integral $\int_{1}^{\infty}
               e^{-xt} t^{-n}dt$ for large values of $n$},
   journal = {J. Res. Nat. Bur. Standards},
    volume = {62},
      year = {1959},
     pages = {123–125},
   mrclass = {65.00 (33.00)},
  mrnumber = {MR0104347 (21 \#3102)},
mrreviewer = {W. Wasow},
     zblno = {0118.32604}}