Two canonical online references are:

• The Digital Library of Mathematical Functions (http://dlmf.nist.gov/)
  This is official successor of the venerable Handbook of Mathematical Functions by Abramowitz and Stegun.

• The Wolfram Functions Site (http://functions.wolfram.com/)
  An expansive collection of identities and properties of special functions amassed and neatly categorized by Wolfram Research.

Two canonical online references are:

• The Digital Library of Mathematical Functions (http://dlmf.nist.gov/)
  This is the official successor of the venerable Handbook of Mathematical Functions by Abramowitz and Stegun.

• The Wolfram Functions Site (http://functions.wolfram.com/)
  An expansive collection of identities and properties of special functions amassed and neatly categorized by Wolfram Research.

Two canonical online references are:

• The Digigal Library of Mathematical Functions (http://dlmf.nist.gov/)
  This is official successor of the venerable Handbook of Mathematical Functions by Abramowitz and Stegun.

• The Wolfram Functions Site (http://functions.wolfram.com/)
  An expansive collection of identities and properties of special functions amassed and neatly categorized by Wolfram Research.

Two canonical online references are:

• The Digital Library of Mathematical Functions (http://dlmf.nist.gov/)
  This is official successor of the venerable Handbook of Mathematical Functions by Abramowitz and Stegun.

• The Wolfram Functions Site (http://functions.wolfram.com/)
  An expansive collection of identities and properties of special functions amassed and neatly categorized by Wolfram Research.