Some information on hotels and drug tourism in Amsterdam?

I am writing my dissertation proposal and I am looking for some research on hotel industry in Amsterdam and a study that connects drug tourism with hotel business again in Amsterdam. If you can direct me to some sites (or paid ones).
Thanks

You will need to look up Amsterdam directly for that sort of information.

You have a very specific question.
I suggest you call some organisations:

The brancheorganisation for cafes, restaurants and hotels is: http://www.horeca.org/smartsite.dws?id=8 Horeca Nederland. I would call them. The hotel-section is here: http://www.horeca.org/smartsite.dws?id=448

The VVV is the Dutch bureau for tourism. http://www.amsterdamtourist.nl/nl/visiting/praktischeinformatie/contactatcb They may have some information.

The Chamber of Commerce of Amsterdam can be found here: http://www.evd.nl/zoeken/showbouwsteen.asp?bstnum=48830&location=

The last could be the city council: http://www.amsterdam.nl/

Start with the Horeca Nederland and the Chamber of commerce