“…Topics #6 and #7 are close to the others, which means it represents one common issue: emissions and environment issues for shipping sustainability, including ship emissions [72][73][74][75][76], truck and intermodal emissions [77], emission regulation and policy [1,10,78,79], and emission calculation [80]. Topics #9, #10, #11, and #13 indicate the external costs, energy, and efficiency issues in sustainability for shipping companies by optimizing their transportation routes and networks: shipping networks to minimize external cost [71], alternative sources and renewable energy [81,82], energy efficiency [83] in shipping, and fleet deployment for sustainable collaborative transportation [4]. Topics #2 and #5 are close to the others, indicating the impact of vessels' pollution on land, such as port-city [1,77] and emission of inland shipping [80].…”