what is American Imagism?

what is American Imagism?
要英文的,归纳得精简点哦,要定义,特点,和举例说明：代表作家例子一两个.总觉得自己归纳得不好,认真回答啊,读书的事情不是开玩笑的哦.

定义a literary movement launched by British and American poets early in the 20th century that advocated the use of free verse,common speech patterns,and clear concrete images as a reaction to victorian sentimentalism.
代表作家及作品ezra pound:in a station of the metro,hilda doolittle:oread,william carlos williams:the red wheelbarrow
原则：1.content should be presented directly,through specific images where possible.
2.every word should be functional,with nothing included that was not essential to the effect intended.
3.Rhythm should be composed by the musical phrase rather than the metronome.