Review paper: “The role of purchasing and supply management in diffusing sustainability in supply networks: a systematic literature review”
Comments to the authors
Summary: the manuscript investigates the extant literature on Purchasing and Supply Management (PSM), intending to systematise the knowledge on how sustainability is diffused in the Supply Chains (SC) by building a framework that matches the PSM process and the sustainable sourcing and supply management practices, both identified form the literature. The topic is attractive from a research perspective as it is underexplored and from a practical perspective, as firms need guidance in the transition towards sustainability to switch from arm-length practices to truly sustainable ones. There are some concerns about the scope of the research, the methodology, the discussion and the contribution. I think these concerns are worthy of the authors’ attention in the next edition of the manuscript.

Detailed comments for each seciton
Title: the title clearly states the content of your work. It is though unclear whether the term “supply network” applies to your work. Throughout all the sections, it appears to be used as a synonym for “supply chain”, while they are not. Please clarify what you mean, as supply networks entail the observation of different parameters (e.g.: network centrality, betweenness etc.) that seem out of your scope.

Abstract: the abstract is well written and clearly summarises the paper’s content. Again, the terminology is ambiguous. The first sentence, in which the motivation for the work is laid out, mentions first-tier suppliers: why is that? It’s not as if they have been taken into consideration or attributed a specific role towards any other tier or focal company.

Introduction: one concern relates to the literature gap identified and the scope of your work. On pages 2-3, you identify a gap in the insufficient knowledge about sustainability diffusion beyond first-tier suppliers and generally in supply networks. Nevertheless, your work doesn’t address this gap as it doesn’t study the role of first and lower tier suppliers towards the diffusion of sustainability.

Methodology: minor concerns in this section have been raised by the following elements:
- Could the addition of sustainability diffusion keywords have eased the screening process of the papers identified? Maybe some addition could be “diffusion”, “spread”, “collaboration”, or “development”.
- Reporting all the queries utilised would help enhance the research process’s transparency. Jabbour et al. (2019) adopt a similar query definition strategy as yours; you could take this as an example to report your query.
- On page 4, you state that 32 journals have been selected as relevant to your analysis: could you list them?
- On page 5, you identify the final number of papers: is 133 papers a sample size consistent with similar reviews?

Data analysis and coding and Findings: well written and with a good structure.

Discussion: this section generally appears confused and redundant. Many pieces of information are repeated in the different sub-sections, preventing them from allowing a fluent reading. Furthermore, this section is repetitive in some passages, and it also tends to repeat what was already reported in the findings.
A suggestion to improve this section would be to restructure it by removing the third sub-level of titles (e.g., The role of PSM in diffusing sustainability, PSM centrality in diffusing sustainability, etc.) and taking your framework (Figure 10) as a backbone. With this perspective, you could provide insights into why or under what circumstances a specific strategy or practice is preferable. Furthermore, you could add a theoretical discussion for why the major theories that you describe in the findings support the positioning of PSM and its role in the diffusion of sustainability. This could also allow you to develop new future research avenues.
There is another important aspect to be considered, though you actually mention it while reporting the findings of supplier development (page 13): what about the imposition of sustainability practices? Such a change in the discussion could help idetìntifying future research questions that go beyond the identification of research gaps.
Also in this section, you mention different actors of multi-tier SC. Particularly concerning sustainability implementation and diffusion, first-tier suppliers are attributed a different role than focal firms as their timing of adoption has been assessed by Schmidt et al. (2017) to be different, with focal firms being first movers and first-tier suppliers late entrants. Unless you are interested in differentiating the discussion and your framework in terms of tiers, discussing the existence of these tiers is out of scope.
A final remark concerns your framework, particularly the comparison of practices that you report in Figure 10 and Table 2. The summary of practices reported in Figure 10 is misleading, as it appears unclear the reasoning according to which the practices fall under a specific strategy. For example, it appears unclear why “green manufacturing” should be a joint development and co-creation practice. I’d suggest reviewing the bulleted point in Figure 10 or keeping the full names from Table 10.

Conclusions: despite the confusion of the previous section, the conclusions seem well centred. Again, here multi-tier supply chain actors are mentioned though never being discussed.
Instead of simply reporting the methodology as a limitation, I would suggest you to specifically explain how you addressed the potential limitations of the methodology, for example, by better discussing the rigour of research. In fact, I believe that your method was quite solid as even if the starting query was broad and multiple researchers were involved in the screening process of the papers, which, given the numerosity, I believe gave you a quite clear picture of what the literature says about your topic of interest.

References
JABBOUR, C. J. C., DE SOUSA JABBOUR, A. B. L. & SARKIS, J. 2019. Unlocking effective multi-tier supply chain management for sustainability through quantitative modeling: Lessons learned and discoveries to be made. International Journal of Production Economics, 217, 11-30.
SCHMIDT, C. G., FOERSTL, K. & SCHALTENBRAND, B. 2017. The Supply Chain Position Paradox: Green Practices and Firm Performance. Journal of Supply Chain Management, 53, 3-25.

Dear authors, thank you for addressing the comments highlighted by reviewer 1 and myself.

In my opinion, the quality of the manuscript has significantly improved for the following motivations:

1) the introduction explains in a much clear fashion the literature gap you are aiming to contribute to and the need for your SLR;

2) the discussion makes much more relevant observations, and having added the three propositions that link the macro PSM practices to embedded/peripheral sustainability makes the contribution of your work more evident;

3) having discussed how theory can contribute to addressing the literature gaps, again, highlight the relevance of your work in a more clear fashion and makes the contribution more evident.

I want to suggest a few minor adjustments to improve your manuscript further:

1) Since you have significantly restructured the discussion section, there might be some additions to the abstract that could improve its impact. I would suggest you to briefly mention in the abstract that, after you identified and classified practices strictly related to sustainability for each PSM macro category, you have defined which type of sustainability (embedded or peripheral) these PSM practice categories are supporting. You could also mention that you define several future research avenues and theories that can be utilized to pursue them.

2) The findings sections remain well-written and with a good structure. When discussing the different psm related practices (pages 12-15), the examples you mention mostly relate to environmental sustainability. I expected the literature to have something more on social (and ethical) issues, also given by the large share they represent in your sample (Figure 7). If you had not been able to identify specific practices in psm that relate to social sustainability exclusively, I would point that out, as it could constitute a future research avenue.

I hope these comments are useful in improving your work. Good luck with your research.