Originally Posted by BenG
E.E. Smith's "Triplanetary" is the same. The free PG version is the story as it was published in the pulps. The copyright was never renewed for this version.
Later, he revised it a little to tie in with his Lensman series and released it as a book.
The same with his "Skylark of Space", the free versions are the pulp versions.
Skylark he also updated in the early 60's to make reference to modern nuclear tech and Einstein. I love how he addressed the speed of light limit.
"It looks like Einstein's theory was wrong."
Unfortunately, he didn't do the same for the rest of the series.
Lensmen doesn't have the same issues with tech anachronisms because most was written post-Einstein and he reworked Tri-planetary to add the Prologue sections (Atlantis, WWIII) for its book edition in the 50's.