Celebratio Mathematica

W. W. Boone, W. Haken, and V. Poénaru: “On re­curs­ively un­solv­able prob­lems in to­po­logy and their clas­si­fic­a­tion,” pp. 37–​74 in Con­tri­bu­tions to math­em­at­ic­al lo­gic (Han­nov­er, Ger­many, Au­gust 1966). Edi­ted by H. A. Schmidt, K. Schütte, and H.-J. Thiele. Stud­ies in Lo­gic and the Found­a­tions of Math­em­at­ics 50. North-Hol­land (Am­s­ter­dam), 1968. MR 263090 Zbl 0246.​57015 incollection

W. Haken: “Con­nec­tions between to­po­lo­gic­al and group the­or­et­ic­al de­cision prob­lems,” pp. 427–​441 in Word prob­lems: De­cision prob­lems and the Burn­side prob­lem in group the­ory (Irvine, CA, Septem­ber 1969). Edi­ted by W. W. Boone, R. C. Lyn­don, and F. B. Can­nonito. Stud­ies in Lo­gic and the Found­a­tions of Math­em­at­ics 71. North-Hol­land (Am­s­ter­dam), 1973. Con­fer­ence ded­ic­ated to Hanna Neu­mann. MR 397736 Zbl 0265.​02033 incollection