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American Association of Variable Star Observers
The largest organization for variable stars: provides professional and amateur collaboration, research, and analysis of variable star observations.
http://www.aavso.org/
The Cepheid Distance Scale: A History
A critical review of the Cepheid distance scale, from its inception, to the Hipparcos mission and beyond.
http://www.institute-of-brilliant-failures.com/
The Minima of Algol
An article by Alan MacRobert from Sky and Telescope Magazine about the star Algol (Beta Persei) was the first eclipsing variable star ever discovered.
http://skyandtelescope.com/observing/objects/variablestars/article_108_1.asp