From the introduction: "This paper examines the phonological status of laminal sibilants in Chamicuro. Chamicuro is a Maipuran Arawaken language spoken in the Amazonian lowlands of Eastern Peru. The phonemic inventory of Chamicuro sibilants exhibits a very strong symmetry of three affricates and three corresponding fricatives. However, when the laminal alveolar fricative [š̯] is considered, the pattern of distribution becomes more complicated. Specifically, it is very difficult to account for the occurrence of syllable-final [š̯]'s in a simple and elegant way. Two possible solutions are outlined and discussed, and the advantages and disadvantages of each one are evaluated."
"Laminal sibilants in Chamicuro,"
Work Papers of the Summer Institute of Linguistics, University of North Dakota Session: Vol. 34, Article 4.
Available at: https://commons.und.edu/sil-work-papers/vol34/iss1/4