Kemper, K. E. (1996). The cost of free water: Water resources allocation and use in the Curu Valley, Ceará, Northeast Brazil. Water and Environmental Studies, Linköping University.

Kemper, Karin E. The Cost of Free Water: Water Resources Allocation and Use in the Curu Valley, Ceará, Northeast Brazil. Linköping, Sweden: Water and Environmental Studies, Linköping University, 1996.

Kemper, Karin E. The Cost of Free Water: Water Resources Allocation and Use in the Curu Valley, Ceará, Northeast Brazil. Water and Environmental Studies, Linköping University, 1996.