Author's Organization:National Institute of Animal Health Chiba Prefectural Federation of Agricultural Mutual Aid Associations Chiba Prefectural Federation of Agricultural Mutual Aid Associations Chiba Prefectural Federation of Agricultural Mutual Aid Associations
Published: April 15, 1992Received: May 22, 1991Available on J-STAGE: February 15, 2008Accepted: December 11, 1991
Advance online publication: -
Revised: -