#### Volume 6, issue 4 (2006)

 1 P M Akhmet’ev, Smooth immersions of manifolds of small dimension, Mat. Sb. 185 (1994) 3 MR1309180 2 S Bleiler, M Scharlemann, A projective plane in $\mathbf{R}^4$ with three critical points is standard. Strongly invertible knots have property $P$, Topology 27 (1988) 519 MR976593 3 V Carrara, J S Carter, M Saito, Singularities of the projections of surfaces in 4-space, Pacific J. Math. 199 (2001) 21 MR1847145 4 V L Carrara, M A S Ruas, O Saeki, Maps of manifolds into the plane which lift to standard embeddings in codimension two, Topology Appl. 110 (2001) 265 MR1807468 5 J S Carter, M Saito, Knotted surfaces and their diagrams, Mathematical Surveys and Monographs 55, American Mathematical Society (1998) MR1487374 6 T Cochran, Ribbon knots in $S^{4}$, J. London Math. Soc. $(2)$ 28 (1983) 563 MR724727 7 T Fukuda, Topology of folds, cusps and Morin singularities, from: "A fête of topology", Academic Press (1988) 331 MR928406 8 D Gabai, Foliations and the topology of $3$-manifolds. III, J. Differential Geom. 26 (1987) 479 MR910018 9 M Golubitsky, V Guillemin, Stable mappings and their singularities, Graduate Texts in Mathematics 14, Springer (1973) MR0341518 10 F Hosokawa, A Kawauchi, Proposals for unknotted surfaces in four-spaces, Osaka J. Math. 16 (1979) 233 MR527028 11 S Kamada, Surfaces in $\mathbf{R}^4$ of braid index three are ribbon, J. Knot Theory Ramifications 1 (1992) 137 MR1164113 12 S Kamada, Braid and knot theory in dimension four, Mathematical Surveys and Monographs 95, American Mathematical Society (2002) MR1900979 13 A Kawauchi, On pseudo-ribbon surface-links, J. Knot Theory Ramifications 11 (2002) 1043 MR1941684 14 H I Levine, Mappings of manifolds into the plane, Amer. J. Math. 88 (1966) 357 MR0208609 15 J N Mather, Generic projections, Ann. of Math. $(2)$ 98 (1973) 226 MR0362393 16 O Saeki, Y Takeda, Canceling branch points and cusps on projections of knotted surfaces in 4-space, Proc. Amer. Math. Soc. 132 (2004) 3097 MR2063132 17 M Scharlemann, Smooth spheres in $\mathbf{R}^4$ with four critical points are standard, Invent. Math. 79 (1985) 125 MR774532 18 K Tanaka, Crossing changes for pseudo-ribbon surface-knots, Osaka J. Math. 41 (2004) 877 MR2116343 19 K Tanaka, The braid index of surface-knots and quandle colorings, Illinois J. Math. 49 (2005) 517 MR2164349 20 R Thom, Les singularités des applications différentiables, Ann. Inst. Fourier, Grenoble 6 (1955–1956) 43 MR0087149 21 O J Viro, Local knotting of sub-manifolds, Mat. Sb. (N.S.) 90(132) (1973) 173, 325 MR0370606 22 M Yamamoto, Lifting a generic map from a surface into the plane to an embedding into $4$-space 23 T Yasuda, Crossing and base numbers of ribbon 2-knots, J. Knot Theory Ramifications 10 (2001) 999 MR1867105 24 E C Zeeman, Twisting spun knots, Trans. Amer. Math. Soc. 115 (1965) 471 MR0195085