I think your question is flawed.

Facism does not find it's origin in Mein Kampf or with Hitler but with Musolini.

Also, communism is not directly opposed by democracy. One might even argue that the end goal of communism is inherently a democratic society.

Democracy is not an ideology but nothing more then the idea that state power should be held by or at least influenced by the people. It's an ideal rather then an ideology. More like the idea that people should have free speech then a plan on how a country should be governed.

It would be impossinle to reach consensus on an authoritative list, but there is a sort of canon of democratic texts in the corpus of Western political thought.

Strong candidates for inclusion would include:

Thoughts on Government (John Adams)

The Federalist Papers (Hamilton, Madison and Jay)

Democracy in America (de Tocqueville)

Considerations on Representative Government (J S Mill)

This is by no means an exhaustive list, and the texts I've cited have a somewhat Anglo-Saxon bias.

Ultimately, though, I think the best short, concise distillation of democratic principles, as understood in the Western tradition in the 20th century, is the UN Universal Declaration of Human Rights.