Life In 19x19

Hello all, recently in my games, i encountered this situation. I searched for josekipedia and kogo for possible continuations but didnt encounter many. How would you answer as black? After move 14? http://eidogo.com/#2LqltYnKH Would you indicate some of the variations or answers to white invasion? Or is there a website or youtube video that gives some ideas? Thank you all for your help in advance.

m4, connect your stones.

M4. White gets some territory from the invasion - White can do it with this shape.

But black gets influence on the outside.

You will probably get sente and can play first on the left, so I think white's invasion is too early.

Thanks for replies! I encounter this situation so often..

Just to be clear, M4 is good in this situation, but later in the game or with different stones around, a different move may be better. M4 trades territory for influence, and here with the board wide open that influence is worth a lot in what was white's area of influence. Later on, it may just be facing a strong white position and be worthless.