dynamics crm 2011 - Unable to add "Created On" field to Information Form on "Article" Entity -

I am working on Dynamics CRM 2011 (Rollup 8). I want to add the "created" field to the "Article" unit's information form.

I can not see the field in Field Explorer and I'm sure the field has not already been used on the form.

Is there any reason why I can not see the "created" field in the list?

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There are several different forms that can not be modified (too) and it is one of them.

• Article template • case resolution • connection roles • contract template • customer relationship • data map • dialog session • discount list • e-mail attachment • e-mail template • field security profile • note • opportunity off • Opportunity Relationship • Order Off • Process • Publisher • Quick Campaign • Quote Off • Resource Group • Saved View • Security Role • Service • Site • Solution • Unit (Mobile Form) • Unit Group • See

You may not even create a new form for articles (as you may be able with other organizations) I do not think that the solution is currently, There is only one limit.