“…Second motivation examines if make-or-buy decision is relevant in terms of firm's performance; this view is concerned to explore the relationship between firms' innovation or economic results and the use of internal or external source of knowledge (Bönte, 2003;Frenz and Ietto-Gillies, 2009;Leiblein, Reuer and Dalsace, 2002;Montoya, Zárate and Martín, 2007;Vega-Jurado et al, 2008). Lastly, third point of interest analyzes complementarities between internal and external R&D activities; that is, if the productivity of the firm increases carrying out simultaneously both types of activities or, on the contrary, are substitutes Gambardella, 1990, 1994;Becker and Dietz, 2004;Caloghirou, Kastelli and Tsakanikas, 2004;Cassiman and Veugelers, 2006;Cohen and Levinthal, 1989;Schmiedeberg, 2008;Watkins and Paff, 2009) From this evidence, one can deduce the convenience of analyzing R&D expenditure as a concept of heterogeneous composition, which, both at the decision level and for its implications in firms' performance, could raise differences associated with the R&D combinations. Consequently, innovation strategy examined through the combination of internal and external R&D activities should be included in order to consider these heterogeneities.…”