Organizations, institutions and governments are constantly publishing reports. Sometimes these reports are published in the form of a beautiful book, sometimes merely as a pile of paper stapled together, or online, on the internet. Although reports are not scholarly publications, they can still contain important information which can be very useful for all kinds of research projects.
It is often hard to work out when these reports were published or whether they are still available. Libraries also collect reports, but this is often a haphazard undertaking. Usually reports are hard to find in bibliographic databases. That is why we tend to refer to reports and similar literature as 'grey' literature.
You can also search in SmartCat. Many important reports are ‘officially’ published and included in catalogues.
The GLIN (Grey literature in the Netherlands) database contains the titles of all publications by governing bodies, academic institutions and comparable organizations published in the Netherlands.