"A sum of gaussian RVs is another gaussian"

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In my machine learning notes for Gaussian Mixture Models, I see the following statement:

It is common to confuse a mixture of Gaussian with a sum of Gaussians. Note that, a sum of Gaussian RVs is another Gaussian, and therefore unimodel.

This is only true if the sum of Gaussian RVs is a sum of independent Gaussian RVs right? If there is any dependency, does this guarantee that the sum of gaussians is NOT gaussian?