“…LIFO loading or first-in-first-out (FIFO) loading (see, e.g.,Carrabs, Cerulli, and Cordeau 2007;Carrabs, Cordeau, and Laporte 2007;Erdogan, Cordeau, and Laporte 2009;Cordeau, Dell'Amico, and Iori 2010;Li et al 2011), and the pickup and delivery problem with time windows and LIFO loading (PDPTWL) (see, e.g.,Cherkesly, Desaulniers, and Laporte 2015;Alyasiry, Forbes, and Bulmer 2019), for the single-stack case.For the multiple stacks case there are papers on the single-vehicle pickup and delivery problem with multiple stacks (see, e.g.,Sampaio and Urrutia 2017;Pereira and Urrutia 2018), the double traveling salesman problem with multiple stacks (DTSPMS) (see, e.g.,Petersen and Madsen 2009;Felipe, Ortuño, and Tirado 2009;Petersen, Archetti, and Speranza 2010;Lusby et al 2010;Carrabs, Cerulli, and Speranza 2013;Alba Martínez et al 2013), and the double vehicle routing problem with multiple stacks (DVRPMS)(Iori and Riera-Ledesma 2015).…”