In scientific literature both ways are used. Another example is: 'generation of electricity' vs. 'electricity generation'. In other situations, however, 'of' seems to be required: 'addition of sugar' is correct whereas 'sugar addition' is probably not. (I am not a native speaker.) Also, there are situations with nouns that are derived from verbs that don't have a latin origin: for example, 'nation-building' (why use a hyphen?). Here omitting the 'of' is apparently legitimate. However, 'plugging of plugs' cannot be shortened to 'plug-plugging', can it? Is there a correct way for the example in the tile of this question in particular? If so, are there definite rules that explain the correct spelling of the other cases?