Special letters in XML - list ?

Hello all,

from here I found out that XSLT removes special letters put directly into
the XSLT file. Instead one has to insert thoese lettter in a special form
(like 
 for a new line, etc.).

Can somebody tell me how these are called and where I can find a list wich
lists the most common of them so I do not need to ask here all the time?

Karl

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