1. My blog.
2. Unanswered question which has abstract algebra or group theory tag.
3. SQL syntax to query the unanswered question.

SELECT TOP 10
Id as [Post Link], Tags, CreationDate
FROM Posts
WHERE AcceptedAnswerId IS NULL
AND (Tags LIKE '%abstract-algebra%' OR Tags LIKE '%group-theory%')
ORDER BY CreationDate

4. A question which was deleted.
5. Homomorphism between finite abelian group. the form of subgroup, endomorphism to its subgroup, explict.