diff --git a/doc/src/02020-tagging.md b/doc/src/02020-tagging.md
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+## Tagging entries {#sec:thestore:tagging}
+
+A store entry MAY be tagged. A tag is a String which matches the
+regular expression in @lst:tagging:regex
+
+```{#lst:tagging:regex .numberLines caption="Regular Expression for Tags"}
+/^[a-zA-Z]([a-zA-Z0-9_-]*)$/
+```
+
+Tags MUST BE stored in the header section "imag" in the key "tags" as an Array
+of Strings.
+The tags MUST BE sorted in alphabetical order.
+
diff --git a/doc/src/04200-lib-tag.md b/doc/src/04200-lib-tag.md
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+# libtag {#sec:libtag}
+
+The "libtag" library contains functionality for tagging entries.
+
+The following functionality for entries is provided:
+
+* Adding a tag to an entry
+* Removing a tag from an entry
+* Fetching the list of tags from an entry
+* Checking whether a tag is set in an entry
+
+The following additional functionality is provided:
+
+* Fetching all entries which contain a tag
+* Fetching all entries which contain a list of tags
+* Fetching all entries which fulfill a set of tag-requirements (either
+  present, or not present, chained by logical operators)
+