• Journal of the Korean Mathematical Society
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• v.38 no.3
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• pp.669-681
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• 2001

This paper introduces the notions of essential and inessential map for countably $textsc{k}$-set contractive maps. These ideas enable us to establish a Krasnoselskii-Petryshyn compression and expansion theorem in a cone for countably $textsc{k}$-set contractive maps.