Indexes are transcriptions, and errors can occur whenever something is copied.
So you should try to look at the originals themselves, not second or even third hand copies, and always quote details of the sources of your information for others to see. These standards extend these principles to try to improve the quality and reliability of our research data. Permission is granted to copy or publish this material provided it is reproduced in its entirety, including this notice. Because of this, and following on from the general Standards enumerated above, the Society has also now accepted and endorsed an accompanying set of standards from the same source. As before, you may feel that some of them state the obvious - to you, perhaps, but not necessarily to others.