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Submitted on: 28 August 2019.
Revised on: 10 October 2019.
Accepted on: 28 November 2019.
___________________AGRICULTURE ECOSYSTEMS & ENVIRONMENT
Submitted on: 23 November 1999.
Revised on: 12 March 2000.
Accepted on: 02 May 2000.
___________________AGRICULTURE ECOSYSTEMS & ENVIRONMENT
Submitted on: 09 February 2010.
Revised on: 24 May 2010.
Accepted on: 06 June 2010.
___________________AGRICULTURE ECOSYSTEMS & ENVIRONMENT
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http://reply.papertrans.cn/1/11/1013/1013-36.png