Inversion with negative adverbials

In formal English, and in written language in particular, we use negative adverbials at the beginning of the sentence to make it more emphatic or dramatic.

That was exactly my intention when I wrote the following sentences (to make them more emphatic):

- Not only  they read books and magazines related to education but also they watch educational TV programmes and use the Internet for pedagogical purposes. (research paper)

- Only after this, they can fight and emancipate themselves from the oppressors. (individual paper)

However, both of them are wrong. After checking in several sources on the Internet,  I recognized the mistakes and corrected them as follows:

- Not only do they read books and magazines related to education, but they also watch educational TV programmes and use the Internet for pedagogical purposes.
 
- Only after this can they fight and emancipate themselves from the oppressors.
 
Pay attention to the correct version! The word order is inverted: the negative adverbial is placed first, an auxiliary verb follows it and the subject of the sentence comes next.

The inversion of the subject and the verb can take place after a clause that begins with Not until and Only after/if/when.

The inversion can also take place after the following expressions:

- Time adverbials: never (before), rarely, seldom; barely/hardly/scarcely...when/before; no sooner....than

- Only a time expression: only when, only after...

- Negative expressions: under, in no circumstances, in no way...

- Expressions starting with Not...: not a noun, not only.... but also, not until...

- Little with a negative meaning 

Source: http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-88760.php