Changes are made to service literature as new information becomes available on parts, prime products or service procedures. Normally, you are told about these changes in the Engine News. References to these changes are found in the Service Information Retrieval System (SIRS). When you make an adjustment on older machines, remember to check the SIRS for any new information. It is also important to check SIRS if you use old service literature as an information source. Always use the SIRS to be sure that all the information you use is current. Also, when Service Manual changes are printed in Engine News, it's a good practice for you to write the Engine News date on the Service Manual page(s) that were changed. This gives you immediate reference to the updated information.