The development of the lexicographer's task at the very beginning of the Spanish lexicography activity was based on the conveyance of materials from some works to others, as well as on the imposition of some canons in the way of approaching and developing them. In several occasions, the lexicographers have been accused of a lack of originality, even labels as "copy", "plagiarism" or "source" have been used to hold in contempt their works. The relationship between "Tesoro de la lengua castellana o española" (1960) from Sebastián de Covarrubias and "Vocabulario italiano-español, español-italiano" (1920) from Lorenzo Franciosini can help us to understand the lexicographer's task in that period of the origin and development of the Spanish lexicography, to be exact, with the comparison of their microstructures it can be delimited if the first dictionary is present in the second one and it can also be determined in what way it does. With this kind of quantifier and detailed analysis we can know the true relationships that exist between the dictionaries. In addition, we can avoid remaining in partial appreciations that tend to become difficult to prove truths.