This document discusses different types of acronyms, including double acronyms (DAs) and triple acronyms (TAs) which contain internal acronyms (IAs). It reviews literature on acronym definitions and classifications. The authors analyze over 20,000 scientific acronyms to investigate relationships between complex acronyms and Chomsky's generative model. They propose a new model using tree diagrams to show how DAs, TAs, and IAs are constructed recursively according to generative grammar principles. The findings could help linguists understand how acronyms are structured and provide information for researchers, teachers and translators.