Bullock, David (2014). Learn these words first: Multi-layer dictionary for second-language learners of English. http://LearnTheseWordsFirst.com

In this dictionary, the semantic primes of Natural Semantic Metalanguage (NSM) are used to build definitions for 300 semantic molecules. These primes and molecules are then used to define each of the 2000 words in the controlled defining vocabulary of the Longman Dictionary of Contemporary English (LDOCE).