Broken link - http keys

On the page https://payswarm.com/specs/source/http-keys/,
Section 4.2 Message Signature Algorithm, the link for the normalization
spec (http://json-ld.org/spec/ED/20110911#normalization-1) is busted.  Is
there a replacement link?  Thanks, Erich

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Erich Bremer
http://www.ebremer.com