There is also a .pdf document available with the table of contents of Ulmer Seminare, issue 20.

A. Three-line proofs

• Wolfgang Arendt:
  Liouville’s theorem, pp. 3–5
• Wolfgang Arendt and Ralph Chill:
  Pettis’ theorem and very weakly measurable functions, pp. 5–7
• Benjamin Célariès and Isabelle Chalendar:
  Three-lines proofs on semigroups of composition operators, pp. 9–14
• Ralph Chill:
  Short proof of the Ingham–Karamata theorem, pp. 15–17
• A.F.M. ter Elst and Sylvie Monniaux:
  Convergence of eigenvalues, pp. 17–18
• Stephan Fackler, Jochen Glück, and Manfred Sauter:
  On continuously embedded Banach spaces, pp. 19–20
• Jochen Glück:
  On dense subspaces of the intersection of two Banach spaces, pp. 21–23
• Gisele Ruiz Goldstein, Jerome A. Goldstein, Rosa Maria Mininni, and Silvia Romanelli:
  A generalized Trotter product formula, pp. 25–28
• Markus Haase:
  A short and elementary proof of “spectral radius equals norm” for selfadjoint operators, pp. 29–31
• Markus Haase:
  Goldstine’s theorem without topology, pp. 31–32
• Markus Haase, Peer Christian Kunstmann, and Hendrik Vogt:
  On the numerical range of generators of symmetric L_∞-contractive semigroups, pp. 33–39
• Moochan Barnabas Kim, John W. Neuberger, and Wolfgang P. Schleich:
  A perfect memory makes the continuous Newton method look ahead, pp. 41–44
• Jan Prüss:
  A three-lines proof of the vector-valued Jensen inequality, pp. 45–47
• Wolfgang M. Ruess:
  Fréchet spaces with the Schur property, pp. 47–49
• Jürgen Voigt:
  On Green’s function, pp. 51–55

B. Open problems

• Wolfgang Arendt, Dominik Dier, and Stephan Fackler:
  J. L. Lions’ problem on maximal regularity, pp. 57–72
• Wolfgang Arendt, A.F.M. ter Elst, and James B. Kennedy:
  Can one hear the shape of a drum? – 50 years later, pp. 73–76
• Guy Cohen and Michael Lin:
  The numerical range of Ritt contractions, pp. 77–80
• Guillermo P. Curbera and Werner J. Ricker:
  Multipliers for spaces of unconditional series in the Hardy spaces H^p(D), pp. 81–84
• Stephan Fackler:
  Regularity and maximal regularity, pp. 85–87
• Stephan Fackler:
  The angle problem for the H^∞-calculus, pp. 87–88
• Jochen Glück:
  Is the peripheral spectrum of positive operators cyclic?, pp. 89–95
• Batu Güneysu:
  The BMS conjecture, pp. 97–101
• Antoine Henrot:
  Two open problems in spectral theory, pp. 101–105
• Bernd Kawohl:
  Two dimensions are easier, pp. 107–112
• Pedro J. Miana:
  Fractional convolution product associated to Mittag-Leffler functions, an open problem, pp. 113–118
• Mustapha Mokhtar-Kharroubi:
  Some questions on absorption semigroups on L¹(μ) spaces, pp. 119–124
• Delio Mugnolo:
  Is essential self-adjointness of T^∗T equivalent to essential self-adjointness of TT^∗?, pp. 125–127
• Delio Mugnolo:
  How to project onto convex functions?, pp. 125–127
• Rainer Nagel:
  9 (AGFA-)Probleme: Version 2016, pp. 127–128
• Werner J. Ricker:
  Commutativity of selfadjoint matrices, pp. 129–131
• Manfred Sauter:
  How twisted can a Jordan curve be?, pp. 133–140
• Vincenzo Vespri:
  Quasilinear evolution problems: Sharp estimates on the kernel estimates and Harnack estimates, pp. 141–148

C. Research articles

• Wolfgang Arendt and Marcel Kreuter:
  Mapping theorems for Sobolev spaces of vector-valued functions, pp. 151–170
• Wolfgang Arendt, Stefan Kunkel, and Markus Kunze:
  Diffusion with nonlocal Robin boundary conditions, pp. 171–195
• Anna Dall’Acqua and Klaus Deckelnick:
  An obstacle problem for elastic graphs, pp. 195–210
• Dominik Dier:
  Non-autonomous forms and invariance, pp. 211–223
• Stephan Fackler:
  Non-autonomous maximal L^p-regularity under fractional Sobolev regularity in time, pp. 225–245
• El-Mennaoui Omar and Laasri Hafida:
  On evolution equations governed by non-autonomous forms, pp. 245–254
• Paweł Keller and Iwona Wróbel:
  A very fast, numerically stable, and accurate algorithm for inverting general tridiagonal matrices, pp. 255–261
• Hynek Kovařík and Delio Mugnolo:
  Schrödinger operators on exterior domains with Robin boundary conditions: heat kernel estimates, pp. 263–281
• Vincent Laurent:
  An alternative proof of the Faber–Krahn inequality, pp. 281–287
• Alexander Nerlich:
  Asymptotic results for solutions of a weighted p-Laplacian evolution equation with Neumann boundary conditions, pp. 289–306
• Manfred Sauter:
  Uniqueness of the approximative trace, pp. 307–331
• Frank Steiner:
  Do black holes exist in a finite universe having the topology of a flat 3-torus?, pp. 331–351
• Vicente Vergara and Rico Zacher:
  Stability, instability, and blowup for time fractional and other non-local in time semilinear subdiffusion equations, pp. 353–372