I've been looking for reading texts appropriate for B1 students. In this process, I have come accross with some Internet sites that use readability formulas to place texts in a given CEFR level. However, the results do not always coincide with the opinions of experts, particularly because it seems that the words that English speakers find most difficult are the easiest ones for Spanish speakers due to the Latin origin of those words. Are the results gotten from this kind of sites trustworthy for this purpose?