Swedish: An Essential Grammar, 2nd edition

De fabriker som anställer ungdomar bör hjälpas. (restrictive)
(Only) those firms employing young people should be helped.
Fabrikerna, som anställer ungdomar, bör hjälpas.
The firms, which employ young people, should be helped.
3 When the determinative is used without a noun de som is now accepted
as an object form for dem som:
Jag kände ingen av de som/dem som var där.
I knew none of those who were there.
Samhället straffar de som/dem som bryter mot lagen.
Society punishes those who break the law.
5.9
5
Pronouns
88

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Relative pronouns
Relative pronouns introduce a subordinate (relative) clause, referring back
to a correlative in the main clause:
Han är en vän
som man kan lita på.
correlative 
↵
He is a friend
whom one can rely on.
Relative pronouns include:
som
the most frequent relative pronoun which, who, what, that