There have also been several linguistic studies of Nheengatu more recently, such as Borges (1991)’s thesis on Nheengatu phonology and Cruz (2011)’s detailed paper on the phonology and grammar of Nheengatu. She also studied the rise of number agreement in modern Nheengatu, by analyzing how grammaticalization occurred over the course of its evolution from Tupinambá (Cruz 2015). Cruz (2014) also studies reduplication in Nheengatu in detail, as well as morphological fission in bitransitive constructions. A proper textbook for the conducting of Nheengatu classes has also been written. (Navarro 2011). Lima and Sirvana (2017) provides a sociolinguistic study of Nheengatu in the Pisasu Sarusawa community of the Baré people, in Manaus, Amazonas.