"Alb"
I only have three, and of course one's the #4 (Bristol Fighter). I'd buy others in a heartbeat as they are full of great quality photos that I've never seen elsewhere. My others are #10, Nieuport Aircraft of World War One and #2, The German Army Air Service in WWI, and they too have some great photos.
According to a list in the back of #10 there were 10 available. The four you are missing are titled as fol:
#7 Air War Over Great Britain by Ray Rimell;
#8 German Aces of WWI by Alex Imrie;
#9 World War One in the Air by Ray Rimell; and
#10 is the Nieuport one above by JM Bruce.
I believe all of mine were found in a second hand book shop many years back; my Nieuport one has a pencilled price of $1.00 on the inside front cover, now that's "bang for the buck"!!
Cheers,
Lance