== Eksterne henvisninger ==
* Excerpts from the first edition of ''Spacetime Physics'', and other [http://www.eftaylor.com/download.html#special_relativity resources posted by Edwin F. Taylor] {{Webarchive|url=https://web.archive.org/web/20120506020539/http://www.eftaylor.com/download.html#special_relativity |date= 6. maj 2012 }}
* [http://www.physics.ucsb.edu/~gravitybook/ James Hartle's gravity book page] {{Webarchive|url=https://web.archive.org/web/20110725093150/http://www.physics.ucsb.edu/~gravitybook/ |date=25. juli 2011 }} including Mathematica programs to calculate Christoffel symbols.
* Andrew Hamilton's [http://casa.colorado.edu/~ajsh/phys5770_08/notes.html notes and programs] {{Webarchive|url=https://web.archive.org/web/20080211161918/http://casa.colorado.edu/~ajsh/phys5770_08/notes.html |date=11. februar 2008 }} for working with local tetrads at U. Colorado, Boulder.
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