Higher education in Spain has to deal with constant troubles and uncertainties due to the economic crisis. high rates of unemployment in young people. lack for study habits in secondary school and legal fluctuations. This uncertain environment does not foster student effort and it is behind the important rates of abandon in higher education. https://ujnvobmnlhgvw.timeblog.net/70682751/economic-performance-evaluation-of-natural-gas-vehicles-and-their-fuel-infrastructures