Types of Oil recovery?

Hi,
we know there 3 are Methods of Oil recovery
1)Primary recovery
2)Secondary recovery
3)Tertiary recovery

I have googled for the same but i find diffrent Answers.
some people say Gaslift is Secondary recovery
Gas Injection / Water Injection is Tertiary recovery

Can you Explain both of this cases what happens in this.
which comes in Primary & which comes in Tertiary recovery


Thanks in advance.