Articles (2002-2009)

The infiniteness of the SAGBI bases for certain invariant rings, Osaka J. Math. 39 (2002), 665-680.

A condition for finite generation of the kernel of a derivation, J. Algebra 262 (2003), 391-400.

A counterexample to the Fourteenth Problem of Hilbert in dimension four, J. Algebra 279 (2004), 126-134.

A finite universal SAGBI basis for the kernel of a derivation, Osaka J. Math. 41 (2004), 759-792.

A generalization of Roberts' counterexample to the fourteenth problem of Hilbert, Tohoku Math. J. 56 (2004), 501-522.

A counterexample to the fourteenth problem of Hilbert in dimension three, Michigan Math. J. 53 (2005), 123-132.

Fields defined by locally nilpotent derivations and monomials, J. Algebra 293 (2005), 395-406.

Hilbert's Fourteenth Problem and algebraic extensions, J. Algebra 309 (2007), 282-291.

Hilbert's Fourteenth Problem and algebraic extensions with an appendix on Roberts type counterexamples, Acta Math. Vietnam 32 (2007), 247-257.

A generalization of the Shestakov-Umirbaev inequality, J. Math. Soc.Japan 60 (2008), 495-510.

A simple proof of Nowicki's conjecture on the kernel of an elementary derivation, Tokyo J. Math. 32 (2009), 247-251.

Automorphisms of a polynomial ring which admit reductions of type I, Publ. Res. Inst. Math. Sci. 45 (2009), 907-917.