“…Each task is necessarily performed for a certain duration, which can be requested using either a fixed constant ( Cappanera et al, 2018 , Gomes and Ramos, 2019 , Liu et al, 2017 , Maya Duque et al, 2015 ) or a flexible range ( Mosquera et al, 2019 ). Yuan et al, 2018 , Shi et al, 2018 assume that the service duration is a random variable with known probability distributions, while Shi et al (2019) describe an uncertainty set for the service duration. Mosquera et al (2019) define the lower and upper bound of the duration ( ) for each visit t , such that a visit always has a minimum and maximum duration of and time units, respectively.…”