Navigation Part   

The navigation part is composed of buttons which can be inactive or active:

 Inactive buttons are present in the page to preserve an homogeneous structure, but also to give information about the existence of a preceding, next or upper page. They are the following:

 Active buttons lead to another page. They are the following:

	back button	up button	next button
link to:	the previous page	the head of the chapter	the following page