Morgan, C. (1996). “The Language of Mathematics”: Towards a critical analysis of mathematics texts. For the Learning of Mathematics, 16(3), 2–10. doi:10.2307/40248208
Also Morgan, C. (2005). Word, definitions and concepts in discourses of mathematics, teaching and learning. Language and Education, 19(2), 102–116.
I am not sure what education level you are referring to - primary, secondary, tertiary. Some colleagues and I did some work a few years ago on teacher education in mathematics and approached its teaching using a metaphor of "Mathematics as a Language". I have provided the publication details below - but am not sure whether or not this is the angle you are taking. Regards, Kevin
Larkin, K., Jamieson-Proctor, R., & Finger, G. (2012). TPACK and Pre-Service Teacher Mathematics Education: Defining a Signature Pedagogy for Mathematics Education Using ICT and Based on the Metaphor "Mathematics Is a Language". Computers in the Schools, 29(1-2), 207.