SageMath

URL: www.sagemath.org
Contact: wstein@ucsd.edu

SageMath (formally known as SAGE) is free and open software that supports research and teaching in algebra, geometry, number theory, cryptography, etc. SAGE includes the following software: GAP, Maxima, Singular, PARI, MWRANK, NTL, Numeric, Python, IPython

Citation (https://wiki.sagemath.org/Publications_using_SAGE):

@manual{SAGE,
  key          = {SageMath},
  author       = {The Sage Developers},
  title        = {{S}ageMath, the {S}age {M}athematics {S}oftware {S}ystem ({V}ersion x.y.z)},
  note         = {{\tt http://www.sagemath.org}},
  year         = {YYYY},
  }