[Eeglablist] not removing the last ICA artifacts

[Xi Zh]

Hi all,
I'm using ICA (independent component analysis) with "runica" to remove
artifacts in my EEG data. I saw the video of Mike X Cohen
https://www.youtube.com/watch?v=AKCK7DXa0gY. He explained that he prefers
to remove the first IC components which contain artifacts and that he
prefers not to remove the other components. My question is If I have 32
electrodes and I run ICA to give me 32 components. Then I check and find
that the first 4 components contain artifacts and I remove them. Then i
find that the 31st and 19th component contain artifact but I don't remove
them. Is this correct? If it's correct, does anyone have a reference
(paper) for this.

many thanks for your help in advance