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On the range of nonlinear operators with linear asymptotes which are not invertible. Comment. Math. Univ. Carolinae 15 (1974). 415-428. 
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Zbl 0296.35038[3] D. G. DE FIGUEIREDO: 
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Zbl 0259.35036[6] G. HETZER: 
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Zbl 0316.47041[7] G. HETZER: 
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An application of generalized degree to a class of nonlinear problems. Proc. Symp. Functional Anal., Liège (1971). 
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Some bifurcation theory for $k$-set-contractions. Proc. London Math. Soc. (3) 27 (1973), 531-550. 
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