@misc {proofwiki,
  author="{Proof Wiki}",
  url="https://proofwiki.org/wiki/Continued_Fraction_Expansion_of_Euler%27s_Number"
}

@book{khinchin,
  title={Continued Fractions},
  author={Khinchin, A.I.A. and Eagle, H.},
  isbn={9780486696300},
  lccn={97008056},
  series={Dover books on mathematics},
  year={1997},
  publisher={Dover Publications}
}