- Editions

Which edition is it that you are going to use and which is available? Are there different editions?

You must always check which edition you are to use, since different editions can vary considerably. On the other hand, it is not always certain that different editions exist. If there are several different editions of a book, it is usually best to use the most recent. If there are many editions, it usually means that a book is considered important.

Are there also different editions on the Internet?

Concerning resources on the Internet, it is often continually updated without the author specifying exactly what was changed. It will show only the date of the last changes. It is therefore difficult to know how much of the material has been updated.