1. Abate D, Belete S, Wegi T, Usman S, Wamatu J, Duncan A (2012) Characterization of the livestock production systems and the potential of feed-based interventions for improving livestock productivity in Sinana district, Bale highlands, Ethiopia. International Livestock research Institute (ILRI), Addis Ababa, p 24
2. Adegbidi HG, Briggs RD, Volk TA, White EH, Abrahamson LP (2003) Effect of organic amendments and slow-release nitrogen fertilizer on willow biomass production and soil chemical characteristics. Biomass Bioenerg 25:389–398
3. Allcock KG, Hik DS (2004) Survival, growth, and escape from herbivory are determined by habitat and herbivore species for three Australian woodland plants. Oecologia 138:231–241
4. Azene B, Birnie A, Tengnas B (1993) Useful trees and shrubs for Ethiopia: identification, propagation and management for agricultural and pastoral communities. Swedish International Development Authority, Nairobi
5. Baum C (2008) Stata Tip 63: modelling proportions. Stata J 8(2):299–303