The December 2021 issue of Networks addresses both theoretical and algorithmic advances for a variety of network optimization problems. The specific contributions detailed in this issue include
• two articles addressing effective delivery (within specified time-windows) using trucks and drones,
• solution procedures for minimum cost flow problems with conflicts,
• investigation of two-tiered delivery problems with robots used in the second tier,
• solution methods for a multi-trip vehicle routing problem with time windows,
• a Lagrangian-based algorithm for solving team orienteering problems,
• an algorithm for large-scale multicommodity flow problems based on an invisible-hand heuristic,
• a neighborhood search approach for an integrated train blocking and shipment path problem.
We trust that the readership of INFORMS will find these articles to be of interest.
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Douglas Shier
Bruce Golden
Editors-in-Chief, Networks
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