Discussion and conclusion
The core contribution of this paper is the presentation of a framework for linking sustainable-oriented innovations and relationship management in sustainable supply chains. This can be positioned in related research on sustainable supply chain management as well as sustainable innovation. On the sustainable SCM side, we position our research as a contribution to the much discussed relationship aspects. In many of the major frameworks proposed in related research (Seuring and Müller, 2008a, b; Pagell and Wu, 2009) as well as recent literature reviews (Gimenez and Tachizawa, 2012; Touboulic and Walker, 2015), related arguments are posited. However, a concrete operationalization of relationship management is still lacking. This is the particular research gap we address in this paper. In detail, linking resource investments, collaboration, and governance allows a comprehensive analysis, where the cases provide some initial evidence of the applicability of this framework. We specify inter-organizational relationships in sustainable supply chains. While relationships are an important part of the research on sustainable supply chain management (Pagell and Wu, 2009; Beske and Seuring, 2014), the three elements, i.e. resource investments (Blome et al., 2014; Huq et al., 2014), collaboration (Touboulic and Walker, 2015; Beske et al., 2014), and governance structures (Pilbeam et al., 2012), have so far been treated separately. Combining them into one analytic framework allows a deeper analysis as is illustrated in the case studies. This drives the further comprehension of relationships in sustainable supply chain management. We admit, and did so already earlier in the paper, that the interrelation among these three constructs of inter-organizational relationships are not fully explored and analyzed.