The　cooperative　output　regulation　problem　has　been　studied　by　two　approaches:　the　distributed　observer　(DO)　approach　and　the　distributed　internal　model　(DIM)　approach,　respectively.　Each　of　these　two　approaches　has　its　own　merits　and　weaknesses.　Recently,　we　presented　an　overview　on　the　cooperative　output　regulation　problem　by　the　DO　approach.　This　paper　further　surveys　the　cooperative　output　regulation　problem　by　the　DIM　approach.　We　first　summarize　the　constructions　and　the　roles　of　two　different　versions　of　the　internal　models:　the　distributed　p-copy　internal　model　and　the　distributed　canonical　internal　model.　Then,　we　describe　an　integrated　framework　that　combines　the　DO　approach　and　the　DIM　approach.　Extensions　and　variants　of　the　DIM　and　their　applications　will　also　be　highlighted.　©　The　Author(s),　under　exclusive　licence　to　South　China　University　of　Technology　and　Academy　of　Mathematics　and　Systems　Science,　Chinese　Academy　of　Sciences　2024.