inducks issue dates

[Ola Martinsson]

Hi !

I've been comparing the issue dates in inducks versus the issue dates in 
  Gerbers photo journal books for the Dell Giants. Some of these issues 
have different issue dates in these two sources.

The ones that differ are

title			Gerber	Inducks
Vacation Parade  1	6-50	7-50
Vacation Parade  2	6-51	7-51
Vacation Parade  3	6-52	7-52
Vacation Parade  4	6-53	7-53
Vacation Parade  5	6-54	7-54
Picnic Party   	 6	6-55	7-55
Silly Symphonies 6	8-55	8-56
Christmas Parade 8	11-56	12-56
Picnic Party   	 8	6-57	7-57
Christmas Parade 9	11-57	12-58

Does anyone know what is the correct issue dates for these issues ?

On the few Giants that I have I can only determine the year, it's 
printed on the inside of the front cover. Where does the information 
about the issue date come from ?

Ola in a cloudy Stockholm +7