How can I cite a workbook? I want to cite someting from this workbook. How can I cite it? The year is 2009 but what should I put between brackets if there is no specific author?
I would treat it as an online resource since it is not published and might be replaced by a newer version at some point. To cite this, you don't need an author but make sure you state the date when you retrieved the resource. In BibTeX it is done using @misc entry for example. 

Another, but less formal, possibility is that instead of a reference, you use a footnote where you will place an URL and the date you retrieved the resource.