 So now that we've talked about what authority control is, let's talk for a minute about why it's important. There are a few different functions that authority control serves for a library catalog and a few different reasons why it's useful. One of these is called disambiguation. This can be useful for telling apart, for example, different people who have the same name or similar names or, for example, words that can be used to mean different topics that are used as subject headings. For example, if you had three men who all wrote books using the name John Smith and that's how it appeared on the title page, you would need to provide an authorized access point that would allow library patrons to distinguish between these three men. So one of them might have a middle name that starts with P and so you can go include his middle initial in the authority record. If two of them have the same middle initial, you might need to go further and use a birth date or death date if it exists if they're not alive anymore to distinguish between them. So John P. Smith, John S. Smith who was born in 1969 and John S. Smith who was born in 1982, they are all different people and authority control and authority records allow you to distinguish between them even if they all use the name John Smith when they were writing. Another function of authority control is called co-location and this, instead of distinguishing between different people or different subjects, this brings together everything that is written by a particular person or everything that is about a particular subject. For example, if you had a person whose name appeared differently on the title page, for example, the first thing they published maybe was the dissertation. They used the middle initial and it was John P. Smith but then later when he published books it just was John Smith and you want your patrons to be able to know that these two items are written by the same person, even though he used his name differently and therefore it appears differently in the title and statement responsibility field, you would use the authorized access point. So if the authorized access point was Smith, John P., you would use that in your 100 field regardless of how the name appeared on the title page. Another useful thing about authority control is that authority records usually contain cross references. This can be helpful if your patron is doing a search in the library catalog but they don't know the authorized access point. If your system makes full use of cross references and sadly not all catalog systems do, but if it does, if your patron typed in Roosevelt comma Teddy looking for something either by or about Teddy Roosevelt and if your authority record has a cross reference that directs them from Roosevelt comma Teddy to Roosevelt comma Theodore, then your authority record and authority control will have done its job in helping your patrons find what they're looking for. So those are the basic functions of authority control and why it's important.