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According to this article, Virtanen published the method in 1943. If so, it was in use long before he published it; according to the Swedish encyclopedia Nationalencyklopedin the method was introduced in Sweden in early 1930s. // Habj 02:23, 30 January 2006 (UTC)
Here is a magazine from May 28th 1932, where writings by Virtanen about is methods are mentioned.  At the top right part of the page, it says in italics (my translation)
Nr 29. The A. I. V. fudder, by ARTTURI I. VIRTANEN, part I. The theoretical principles
of the A. I. V.-method, plus observations from its use. Price 50 öre.
Nr. 30. The A.I.V. fudder, by ARTTURI I. VIRTANEN, part II.
How to make the A. I. V. fudder. Price 50 öre.
Also, recieving the Nobel prize two years after publishing the data sounds incredible. Since I currently have no idea how to find the correct year, I remove the year mentioned for now. // Habj 02:46, 30 January 2006 (UTC)
the method was patented in 1932, see  number 5. // Habj 03:17, 30 January 2006 (UTC)