This is rare, but on occasion there have been errors in our products and when we discover any of these we immediately email all customers who have purchased the product. Most of these are not critical errors, meaning, we have only found a few words in our word list products that were misspelled over the years. As a 30+ year company, many of our products are in their third or fourth edition and have been editing many, many times over the years. You may find it interesting to know that there are even errors in the dictionary, but a large company that mass-produces books does not have the luxury as we do of being able to notify every customer who has purchased from them. We take errors very seriously and take all measures to contact customers with corrections. Please make sure that hexco.com is on your approved senders list in your email and feel free to email us anytime regarding your product purchase if you are concerned with any possible errors. We would also like to hear from you if you find any errors in our products or have questions on information that is presented so that you we may correct them right away.