Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:These include issues such as the internalisation and pricing of knowledge assets (Markusen, 1984; 2002), the advantages of horizontal (Horstmann and Markusen, 1992; Markusen and Venables, 2000) and vertical integration (Aghion and Tirole, 1997; Grossman and Hart, 1986), and the advantages of subcontracting and licensing versus FDI (Ethier and Markusen, 1996; Helpman and Grossman, 2002; Horstmann and Markusen, 1987; Markusen, 2002).
Category: