2:1 The SWAMP THING #44("Bogeymen")
Joćo Paulo Cursino pointed out to me the writing on the wall: "Len and Berni were here 1972". Indeed. Len Wein and Berni Wrightson created S.T. in 1972.
6:2 ST was able to visit the afterlife this way in SWAMP THING ANNUAL #2.
?:? Alec and Linda Holland were last seen in Heaven in ANNUAL #2.
They are next seen in issue #78.
We saw Arkham Asylum, the Joker, and TwoFace in #52.
?:? CIA officer Dwight Wicker and agents Skinner, Cutley and Foley almost killed Swampy in #53. Swamp Thing killed them in #63. They are next seen in hell in #75.
??? refers to the roses which Swampy killed him with.
?:? Constantine tells Woodrue to keep talking because he is being recorded, and John will steal the recording later (?:?) and view it in a video store in the next issue.
COMMENT: Killer Croc appears in the Woodrue story in SECRET ORIGINS #23. There we see Croc recuperating from the paralyzing gas which Batman sprayed him with.
COMMENT: Batman is no stranger to the Swamp Thing. Dr. Huntoon next appears in #70.
COMMENT: SWAMP THING ANNUAL 3 was published after SWAMP THING #65 and before this issue.
COMMENT: In 2004, DC Comics collected issues 65-70 in the trade book "Swamp Thing: Regenesis".