Another inconsistency in English - help me please

[english_learn]

The following skills required for job advancement.

1. In this sentence why we can not say “Skills are required” ?
2. I think “skills required” is wrong. The word “are” should be included.
3. If you think the above sentence is correct please tell me the grammar rule.

[Tdol]

However, the italics in the post suggest to me that the original text was did not have the following in it. As a heading or title, Skills required for job advancement would be fine.