Iraj Kalantari Larry Welch A blend of methods of recursion theory and topology: A Pi<sub>1</sub><sup>0</sup> tree of shadow points. 991-1008 2004 43 Arch. Math. Log. 8 http://dx.doi.org/10.1007/s00153-004-0244-0 db/journals/aml/aml43.html#KalantariW04