## 6 Conclusions  
The quick development of the Industry 4.0 notion reveals the necessity of investigating the effects of the associated technologies on SCs. Moreover, to retain the market share, eliminating the non-value added activities by Lean principles could lead to a great competitive advantage [80]. Therefore, the present study focus on the opportunities created by using both Lean and Industry 4.0 technologies in SC. To this end, [19] mentioned that the application of Lean is mostly addressed from the side of single SC echelons because it is in conflict with the concept of Lean at the SC level. However, the results of the present work, by doing a comprehensive SLR, indicate the power of Industry 4.0 in combination with Lean principles to achieve a Leaner SC. In particular, SC members can improve trust and information sharing by using Industry 4.0 technologies such as BDA, IoT, CC, BC which leads to reducing over-production, over-processing, and inventory waste in multiple SC echelons. Additionally, revolutionizing the information sharing structure in SCs can facilitate the use of other Industry 4.0 technologies to pave the way for implementing the Lean approach in all the processes. For instance, data sharing and data protection provided by BDA, CC, IoT, and BC can increase trust and transparency. It leads to accelerating the AM adoption in different SC parts by providing a secure way to protect the license of innovative ideas to produce by AM. As a matter of fact, AM by reducing lead times can help to eliminate unnecessary motion, transportation, waiting, as well as to reduce defects. Therefore, the present work illustrates the capability of the combination of Industry 4.0 technologies and Lean principles to enhance SC structure by studying that from different perspectives.  
There are some limitations in the present research. Despite the concerted efforts to follow a scientific procedure for setting the keywords for searching in scientific databases, there is a possibility of missing some relevant works. Furthermore, in the present contribution, the authors searched the keywords only in Scopus. Therefore, to alleviate these limitations, the present SLR completed with snowballing to be sure about covering all the relevant works. Additionally, in proposing the results and gaps it does not consider the impact of industry size on real practice adoption.  
Although Section 4.2 and Table 3 already show some research directions about the investigated topic out of the SLR, the following suggestions for future works can be added. In this regard, with more development of Industry 4.0 in different aspects of SC, it could be valuable to assess the other Industry 4.0 technologies excluded from the present work to enhance the results of the SLR. Moreover, searching in other databases might lead to finding some newly published works in this field. Additionally, it could be beneficial to classify the results of the performed literature review based on their applicability from the perspective of different industry sizes. In fact, different industry sizes do not have the same resources to invest in constructing Lean DSC. Therefore, future research should address this issue by defining the most appropriate roadmap for each industry size. Moreover, depending on the industry size, relevant SCs can have different requirements. This should be considered by addressing the most appropriate solutions based on Lean DSC.  
Conceptualization, M.M.; methodology, M.M. and A.C.C.; formal analysis, M.M.; investigation, A.C.C. and C.R.; writing--original draft preparation, M.M.; writing--review and editing, A.C.C.; visualization, M.M.; supervision, C.R., A.C.C. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data that support the findings of this study are available from the corresponding author.  
No potential conflict of interest was reported by the author(s).