Getie Gelaye. Peasants and the Ethiopian State: Agricultural Producers’ Cooperatives and Their Reflections in Amharic Oral Poetry; A Case Study in Yetnora, East Gojjam, 1975-1991. Hamburg: Lit, 2000.
On däbo (agricultural work group) and yäsəra zäfän (work song), see esp. pp. 59-62: