Not completely sure about the aim and type of research you are planing.

Data collection

You could try to find official data /statistics on the prevalence of national groups (and their size) and organized crime (cases) in Turkey.

Data analysis

You could then link the two variables (e.g., correlation/regression analysis) for different geographical regions or different years/time spans.

Thank you very much ! This is going to be a master dissertation (mainly qualitative and exploratory ). I will try to find the links between organized crime (mafia) and ultranationalist groups (mainly turkish). Additionally I will focus on learning the targets of these groups and their relations with turkish government.

Be serious if your thesis is any good why would these people let you live? David Booth

@David Eugene Booth most likely they don't read and care about this kind of works) This is not a new phenomenon. They let us to live)