Let's just look at the covers, that's easier.
The Million Year Picnic appeared in
That magazine looks to have been quarterly at the time, and that was the summer issue. This is Astounding from that July:
The Earthmen Appeared here in August 1948:
Astounding from that month:
The Third Expedition (originally "Mars is Heaven" appeared here in Fall of 1948:
Astounding from that October:
The Long Years spring 1949:
Astounding from April:
The Martian in November 1949:
Astounding:
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