Acknowledgements I wish to thank my supervisors Dr. Mentore Vaccari and Dr. Angelo MazzÚ, who guided me in the research sharing their knowledge and investigating new topics with enthusiasm. I wish to express my gratitude to the Archetti family and to Prof. Carlo Collivignarelli, who gave me the chance to work on interesting topics and projects. I am deeply thankful to the staff of ACRA NGO in Bongor, Yagoua, Maroua and N’Djamena for their support to my research activity and for their friendly hospitality.
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