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Directly from public TeamCity server:
5.1 and above x last nightly build
5.0.x last nightly build
4.5.x last nightly build
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Sources in JetBrains Subversion repository.
Builds for TeamCity 5.1 x and above and
Builds for TeamCity 5.0.x and
Builds for TeamCity 4.5.x at JetBrains public TeamCity
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