National Geographic 1979 - 2004

Got the whole collections 2 years ago when my neighbour is moving out. Whole collections are clean and in perfect condition. All the book covers are in great shape, There are several missing books throughout the whole collections. The missing books are: '1994 May,' '2000 Sep,' and '2004 Feb to Dec.' Additionally, I found duplicates of '1997 Jan to Apr.' Strangely, there's also a lone '1971 Oct'. The hardcover ones are not included.