Based on the information why is it difficult to study the Amazon river dolphin

Take a look at the lyrics of machaut's ma fin est mon commencement (my end is my beginning): 1. ma fin est mon commencement 2. et mon commencement ma fin 3. est teneüre vraiement. 4. ma fin est mon commencement. 5. mes tiers chans trois fois seulement 6. se retrograde et einsi fin. 7. ma fin est mon commencement 8. et mon commencement ma fin. 1. my end is my beginning 2. and my beginning my end 3. and true tenor. 4. my end is my beginning. 5. my third part three times only 6. moves backward and so ends. 7. my end is my beginning 8. and my beginning my end. the first two lines ("ma " and "et ") are reused to end the poem. in what other line do you see the first line from the poem ("ma ")?