'Cannot find name' after adding external library

[Blaenzo]

Hi,

I added an external library using npm and added a reference in "externalJS" in pbiviz.json, as described here:
https://github.com/Microsoft/PowerBI-visuals/blob/master/Tutorial/ExternalLibraries.md

However, when I try to create a new object I get an error saying that it 'cannot find name' of the package/constructor.

Do I miss somethere here? Do I need add some kind of import statement?

Thanks,

Martijn