Hi Sreiko,
The first thing that you need to determine is what sort of damage you could do to the author, publisher, or distributor(s) of this book by posting the excerpt on-line. There is a pretty good chance that the author is no longer with us, but I am unsure if the publisher had since gone out of business (I saw a few references that the company dissolved in 1979, but I cannot verify this

).
The book is somewhat rare do to its age, and because you are only providing seven lonely pages, I do not really see a blatant copyright infringement, but this is my opinion. It would be rare indeed for a company to press charges against you for use of such an old and obscure manuscript. Internet copyright laws are still being worked out, as they transcend international borders, so individual country laws are hard to enforce. Because you are going to provide the source of the seven pages (and not claiming it is your own work), I feel that you will cover yourself adequately.
I would look at the laws of the country in which you live, and see what they have to say. I can only vouch for US laws on the matter, where I believe that the information in this book became 'public domain' some time ago, which basically says that it can be shared freely between all individuals. See this website:
http://www.copyright.gov/circs/circ22.html
It is interesting that the website had this to say:
"Works First Published or Copyrighted Between January 1, 1923, and December 31, 1949, But Not Renewed · If a work was first published or copyrighted between January 1, 1923, and December 31, 1949, it is important to determine whether the copyright was renewed during the last (28th) year of the first term of the copyright. This can be done by searching the Copyright Office records or catalogs as explained previously. If no renewal registration was made, copyright protection expired permanently at the end of the 28th year of the year date it was first secured."
Again, this is US law, and the book is German in origin, but it would be logical to believe that Neumann's book would fall into this category.
Here is another intersting website on the internet and public domain:
http://en.wikipedia.org/wiki/Public_domain
I hope that I was of some help to you. (BTW, the book title is
In Der Luft Unbesiegt: Erlebnisse Im Weltkrieg Erzahlt Von Luftkampfern , by Georg Paul Neumann; J.F. Lehman
ns
Verlag)
regards,
Darren