Gaute Messel Nafstad Amund Haugseth Vebjørn Høyland Magnus Stålhane An exact solution method for a rich helicopter flight scheduling problem arising in offshore oil and gas logistics. 105158 2021 128 Comput. Oper. Res. https://doi.org/10.1016/j.cor.2020.105158 db/journals/cor/cor128.html#NafstadHHS21