Complex sentence: In 1641, Father Cristobal de Acuña published in Madrid a memoir of his expedition to the Amazon river entitled "Nuevo Descubrimiento del gran rio de las Amazonas", which for academics became a fundamental reference on the Amazon region.
Split into simpler sentences: In 1641, Father Cristobal de Acuña published in Madrid a memoir of his expedition to the Amazon river. The title of the memoir is called "Nuevo Descubrimiento del gran rio de las Amazonas", and it was used by academics as a fundamental reference pertaining to the Amazon region.