Portnyagin, Yu. I.
Merzlyakov, E. G.
Jacobi, Ch.
Mitchell, N. J.
Muller, H. G.
Manson, A. H.
Singer, W.
Hoffmann, P.
Fachrutdinova, A. N.
Article History
Received: 28 July 1998
Revised: 8 February 1999
Accepted: 20 April 1999
First Online: 26 June 2014
Free to read: This content has been made available to all.