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explicitly stated that email address is used in for user name
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example showing easy updating for a list of classes
Detection of courses which appear completed.

If no lecture resource is downloaded and the last modification time to a
resource is over 30 days old, then indicate that this class is likely
completed. This is useful when maintaining a list of classes, to know
which to move out of the "current" classes being periodically updated.
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Updates to description about Coursera.org.
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Improved citation.