Introduction
The world is facing with the increase in natural disasters, wars, and terrorism. Humanitarian logistics, which includes the processes of planning, implementing and controlling the efficient flows for disaster management, plays a crucial role in dealing with various disasters, including natural and man-made disasters. Supply chain resilience refers to the ability of a system to withstand, adapt to, and recover from disruptions. This is of high importance in humanitarian logistics as it helps relief organizations operate effectively in the face of unforeseen challenges. Supply chain resilience refers to the ability to identify potential risk sources and then providing a coordinated solution to reduce supply chain vulnerability. The response of an organization to a disaster is given in three steps: a) The organization receives a warning of a disruption, b) If the organization cannot provide an appropriate solution to avoid the disruption, it leads to a system failure and c) The organization takes actions in the recovery phase to reach its previous performance level. In general, to have a resilient system that can respond well to disruptions, there should be “flexibility”, “agility” and “collaboration between supply chain members”. The recovery phase of supply chain resilience in humanitarian logistics has not been given much attention due to the limited time for providing disaster relief in the response phase. However, since a disaster is an unpredictable event and the system may still face disruptions during a disaster, it is very important to have a strategy for post-disaster system recovery.
The concept of fairness in humanitarian logistics refers to the distribution of relief items equally and fairly among victims. This is essential to maintain peace and social stability during disasters. The sudden increase in demand after a disaster is one of the important reasons for paying more attention to the concept of fairness. Fairness has always been an important issue in humanitarian logistics. Some of the important criteria to measure fairness include penalties for unsatisfied demand, penalties for shortages relative to the demand of each demand point (taking into account the urgent priority of that area), equity and stability in proportion of demand shortage, equity and stability in terms of global dispersion, and minimization of the maximum gap. It should be noted that attention should be paid to the principles of the Sphere project (a set of minimum standards in the field of humanitarian assistance to maintain human dignity during a disaster) to establish fairness.
Resilience and fairness can be considered fundamental concepts in humanitarian logistics. By considering these concepts, relief organizations can more effectively plan and implement their operations during disasters, and respond to the needs of the affected people in a fair manner. This study aims to review the literature on the concepts of resilience and fairness in humanitarian logistics and identify the research gaps.

Methods
In this study, data were collected qualitatively from books and the articles related to resilience and fairness in humanitarian logistics published from 2010 to 2023 and available in online databases including Google Scholar, Scopus and Web of Science. Microsoft Excel was used to analyze the data using the meta-analysis method. 

Results
Fairness and resilience have been challenging issues for relief organizations in recent years. While there has been a growing research on these concepts, there are still significant research gaps. The review of the studies revealed that few studies had focused on multi-objective and multi-layer problems and most of them assumed single-period problems. Additionally, attention to risk-averse approaches for estimating very low uncertainties was at a minimal level. The epsilon-constraint method had been used more than other methods to solve multi-objective problems. Furthermore, the types of disasters and relief items lacked diversity. Insufficient attention had been paid to critical decision-making aspects in humanitarian logistics, such as supplier selection and reservation of relief items, evacuation of affected people from disaster areas, and allocation of doctors in hospitals. The integration of fairness and resilience into humanitarian logistics is still in its early phase.

Conclusion
This review study highlights that despite the importance of fairness and resilience in the humanitarian logistics, numerous research gaps exist. The integration of these two concepts into academic curriculums can lead to increased system resilience in the face of disasters and improve the satisfaction of beneficiaries.

Ethical Considerations
Compliance with ethical guidelines
In this study, no experiments on animal or human samples were conducted. All publication ethics were observed.

Funding
This article was extracted the master’s thesis of Parham Aghayani approved by Tarbiat Modarres University. This study did not receive any grant from funding agencies in the public, commercial, or non-profit sectors. 

Authors' contributions
Conceptualization, methodology, validation, investigation, visualization, resources, review & editing: Aghayani and Nikbakhsh; Writing initial draft: Aghayani; Supervision: Nikbakhsh.

Conflicts of interest
The authors declared no conflict of interest.



References