I don't know if your source shows the original indices for the "O.R.," but they are highly detailed and very helpful with research. To find all the entries on a particular unit in a particular book of the "O.R." look in the index in the back under the state name and it lists all mentioned in that particular book under the state heading by branch of service and unit number. If your source does not include the index for specific books of the set, perhaps it has one overall index that should provide this same service. If the reader only has the name of the commander--common in Confederate units--there is also an appendix in the back of each book that gives the commonly associated name of the commander and a brief cross reference to the numerical name, also.

Another feature I like is that the index for each book gives the first name and middle initial of individuals named in the text, if known. Many of the original writers of the entries in the "O.R." assumed the recipient was familiar with the person named only with the last name, so this feature really helps, especially with names like "Johnson," "Smith," "Jones," etc.

Bruce Nichols