A mi familia, a quienes tantas horas robé pero nunca el afecto "…en fin, que lo que da verdadero sentido al encuentro es la búsqueda, y que es preciso andar mucho para alcanzar lo que está cerca" José Saramago
IX
AcknowledgementsAt this point I look back, and I would like to show my gratitude to all the people that somehow have contributed to this work in one way or another.
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