## 3 Research Methodology
### Material Collection  
This study focuses initially on the review of VRP's application in humanitarian operations with which the search for materials began. From the search, several recurring themes namely the \"_supply and delivery_\", \"_execution_\", and \"_rescue_\" operations were noted. Thus, we narrow the scope of VRP's application further into these three specific humanitarian operations. To our knowledge, no study has been conducted on these three specific humanitarian operations put together in the scope of VRP. Based on the refined scope of the study, reputable review papers are referred to note potential papers that might fit into the scope of this study. Apart from this, an independent search for review materials is also performed through the Google Scholar search engine and the subscribed databases that are guided by the following strategies:  
1. Potential papers are searched with all possible permutations of specific keywords, such as \"_VRP_\", \"_dynamic_\", \"_stochastic_\", \"_disasters_\", \"_search_\", \"_rescue_\", \"_emergency_\", \"_delivery_\", \"_execuation_\", \"_vehicle routing_\", \"_humanitarian_\", and \"_supply_\". The VRP is set apart from other problems, such as covering tour problem that addresses routing, but not particularly addressing the VRP explicitly. However, known combinations of the OR problems, which include routing problems, such as Allocation Location Routing Problem (ALRP) and Location Routing Problem (LRP), are included within the study. Additionally, this also includes intermodal network problem involving multiple types of vehicle as well as cooperative operations among vehicles, such helicopter and land vehicle. 2. The search results are filtered by year, in a decreasing order starting with the year 2020 until the year 2010. For each year, the search results are examined page-by-page of minimal 15 search results pages, even though the topic of the searched papers no longer show any relevance to the scope of the study. Otherwise, the search continues in the ongoing pages until no more topic of relevance is obtained in the search. This process is repeated for the year 2020 at three days interval throughout the search duration in order to ensure that any related work is included in the study. In addition to the papers in [6], the search duration lasted for close to six months (May 2020-October 2020) while reviewing the collected papers in parallel. 3. All of the selected papers are deemed to be potential papers for review judging by the topic, description in the abstract, few last paragraphs of the introduction section, a glance of the methodology and analysis sections, as well as the conclusions. Furthermore, only English written papers are considered for generating a systematic and consistent study. 4. From these promising papers, the literature review section or equivalent sections are particularly screened through in order to search for other promising papers. 5. The resulting papers are then compiled in a Microsoft Excel spreadsheet, where the type and the source of the papers are listed. The source of the papers are then crossed check with the Web of Science (WoS) and Scopus database in order to obtain details of the source, such as the impact factor of a journal and the respective latest quartile performance, with which the quality of the sources is determined. 6. Materials not belonging to any typical sources, such as Ph.D. theses or technical reports, are not immediately dismissed. Instead, a proper check and study towards these materials are performed in order to judge the relevance, quality, and validity of the work. This ensured that the finding of the review study would cover all good materials from various sources. Based on the following material collection method, a total of 123 papers are obtained for review. From a considerably huge bulk of potential materials, many are filtered out, as not all materials are explicit in their work in addressing the application.