 Most difficult are the earliest texts, which in many cases do not give the full grammatical structure of the language and seem to have been used as an "aide-mémoire" for knowledgeable scribes.During the 3rd millennium BC a cultural symbiosis developed between the Sumerians and the Akkadians, which included widespread bilingualism.The influences between Sumerian on Akkadian are evident in all areas including lexical borrowing on a massive scale—and syntactic, morphological, and phonological convergence.