I think it depends on the topic, if you have no competition, a couple of lines can get good positions, but if your subject is very competitive, you should have more text on your page.

PS: Remember to write quality articles or your bounce rates will be very high and will cause you to lose positions.

What you should do is:

There are a few things you can do to increase the chances that they might appear on your pages. First, ensure that long, multi-topic pages on your site are well-structured and broken into distinct logical sections. Second, ensure that each section has an associated anchor with a descriptive name (i.e., not just "Section 2.1"), and that your page includes a "table of contents" which links to the individual anchors.

Maybe the question is: how to create these internal links?

This goes in the table of contents

Anchor Text

This is in the section:

Section 1 Title

More info:
http://www.w3.org/TR/html401/struct/links.html#anchors-with-id

This is done using anchor links within the page source. More information:

http://googleblog.blogspot.com/2009/09/jump-to-information-you-want-right-from.html

http://googlewebmastercentral.blogspot.com/2009/09/using-named-anchors-to-identify.html

just what I was looking for thanks

Thank you very much to you both for your answers.

Question Answered

I have the feeling that I am suffering from negative seo, so there is a way to get a list of links that should remove in the google disavow links tool ?