Violeta D. Baluyut, Area Handbook for Bulgaria
“ Those who have had military service and who have not reached the age of fifty are considered reserves. Officers remain in the reserve until the age of sixty. Various factors—primarily occupational situations, physical condition, and lack of reserve training—operate to erode this force, and those considered useful, or trained, reserves constitute one-half or less of the group. Most of the some 250,000 men released in the latest five-year period, however, are available, physically fit, and familiar with the weapons and equipment in use by the armed forces. ”
