Stuff like this doesn't really get outdated. The science we usually discuss on these forums are so basic and rudimentary that 40 to 50 year old studies often have more than enough information for us to gain understanding of aquaponic systems. Take for example when I was trying to analyze human urine as a source of fertilizer. All the newer studies were talking about such fine details of the urine or were looking at specific aspects that I couldn't get what I wanted. Basically, all the newer studies took for granted what I was trying to learn for the first time. I ended up finding a 30-40 year old paper published by NASA on human urine. The chemistry used in the paper was nearly identical to what I learned in my Chemistry classes (a few numbers or assumptions were off which were revised by newer technology and such), but I would say 98% of it was right on and perfectly useful to me... anyway, rambling, but thanks for sharing, good find! A lot of the information out there is put out by the Extension and that's our job, to help bring information in a useful manner to the general public... who knows you might find stuff I publish through my extension on the web in the next few years (which I am definitely trying to pilot a program at our county office so that the master gardeners know what aquaponics is and how to teach people about it when they need help)