On the rectangular knapsack problem: approximation of a specific quadratic knapsack problem.
Britta Schulze, Michael Stiglmayr , Luís Paquete, Carlos M. Fonseca, David Willems , Stefan Ruzika
Mathematical Methods Of Operations Research, vol. 92, 2020, p. 107-132.

On the rectangular knapsack problem: approximation of a specific quadratic knapsack problem.
Britta Schulze, Michael Stiglmayr , Luís Paquete, Carlos M. Fonseca, David Willems , Stefan Ruzika
Mathematical Methods Of Operations Research, vol. 92, 2020, p. 107-132.