a). Danger on the red planet
b). Death in the Arctic
c). Mystery of the pharaoh
d). Lost in the Amazon
Thanks to that other friend of the blog John Freeman I now have copies of the 2 book covers I was missing
...and John has also pointed out that the books were also published in Spain - link here
So I was delighted that friend of the blog David Ronayne posted this image over the weekend - a bargain that he found at a local book fair...
…so that's a collected edition of all 4 books to look out for - if you come across Death in the Arctic or Mystery of the pharaoh please let me know as I'd love to see those covers.