How do you explain the stability of the Italian system of government between 1945 and 1992?

It is an essay of the subject European Integration in Historical Perspective. It must have a maximum of 2500 words and also contain many references and a bibliography. The topic of the work is: How do you explain the stability of the Italian government system between 1945 and 1992? About this essay I do not have many indications of the professor, only that it must contain an introduction, body, conclusion and bibliography. It is very important that this is well structured and that in the introduction the subject is explained and that you have a short summary of what the essay will be talking about. I will attach examples about essays, to see how it is done.