Labor (2) Employees (2) Backache (2) Lumbago (2) Trabajo (2) Trabajadores (2) Minors (1) Wheels (1) Weights and measures (1) Valuation (1) Social sciences (1) Sleep disorders (1) Psychology (1) Production (Economic theory) (1) Physicists (1) Muscles (1) Job satisfaction (1) Industrial hygiene (1) Indexes (1) Id (Psychology) (1) Health (1) Evaluation (1) Diseases (1) Design (1) Cities and towns (1) Arm (1) Sueño--Trastornos (1) Satisfacción en el trabajo (1) Valoración (1) Evaluación (1)