In this paper, we introduce the concept of a countably asymptotically
?-nonexpansive operator. In addition, we establish new fixed point results
for some countably asymptotically ?-nonexpansive and sequentially
continuous maps, fixed-point results of Krasnosel?skii type in locally
convex spaces. Moreover, we present Leray-Schauder-type fixed point theorems
for countably asymptotically ?-nonexpansive maps in locally convex spaces.
Apart from that we show the applicability of our results to the theory of
Volterra integral equations in locally convex spaces. The main condition in
our results is formulated in terms of the axiomatic measure of
noncompactness. Our results improve and extend in a broad sense recent ones
obtained in literature.