Concerted practice is the most nebulous of the three categories caught by Article 101 TFEU

Concerted practice is the most nebulous of the three categories caught by Article 101 TFEU.
(S.Collino, Competition Law of the EU and the UK (OUP, 7th ed., 2011) 156
Critically discuss this statement with reference to the CJEUs interpretation of Article 101 TFEU.

suggested structure;
1Introduction
2The scope and theory of purpose of EU competition law
3Analyse article 101 elements
4Focus on concerted practice and the cases in regard to it.
5Conclusion.

Note; the referencing system is OSCOLA.