View source for Notes for 6 1's three dimensional invariants

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[[6_1]] is a ribbon knot (drawings by Yoko Mizuma):
{| align=center
|[[Image:6_1_As_Ribbon.jpg|thumb|100px|a ribbon diagram]]
|[[Image:6_1_Ribbon_Sequence.jpg|thumb|isotopy to a ribbon]]
|}

[[Image:6_1_is_doubly_slice.jpg|thumb|135px|right|[[6_1]] has two slice disks, by Scott Carter]] Scott Carter notes that 6_1 bounds two distinct slice disks. He says: "this was spoken of in Fox's Example 10, 11, and 12 in ''a Quick Trip through Knot Theory'' ... BTW, the cover of Carter and Saito's ''Knotted Surfaces and Their Diagrams'' contains an illustration of such a slice disk". A picture is on the right.