fix(citations): systematic audit — 6 corrections in references.md

Findings from full citation audit of all 34 references.md entries:

CRITICAL:
- Knöppel et al. 2015 "Stripe Patterns": arXiv 1502.06686 was a completely
  different paper (Data-Driven Shape Analysis by Xu et al.) — removed from
  papers/. Correct DOI is 10.1145/2767000, not 10.1145/2766890. No arXiv
  preprint exists for this paper.

ERRORS:
- Born, Bücking, Springborn: published 2017 in DCG 57(2) pp. 305–317
  (DOI 10.1007/s00454-016-9854-7); arXiv 2015 was preprint only
- Bobenko, Mercat, Schmies: short title; full title is
  "Conformal Structures and Period Matrices of Polyhedral Surfaces";
  editors Bobenko & Klein (not generic "Computational Approach" book ref);
  pp. 213–226, DOI 10.1007/978-3-642-17413-1_7

COMPLETIONS (missing vol/pages added):
- Pinkall, Polthier 1993: vol. 2(1), pp. 15–36, DOI added
- Bobenko, Springborn 2004: Trans. AMS 356(2), pp. 659–689, arXiv added
- Luo 2004: Commun. Contemp. Math. 6(5), pp. 765–780, DOI + arXiv added

Verified ✅ (no changes needed, 28/34 entries):
Sechelmann 2016, Springborn 2020/2008, Ushijima 2006, Bowers-Stephenson 2004,
Glickenstein 2011, BPS 2015, Schläfli 1858, Erickson-Whittlesey 2005,
Bobenko-Springborn 2007, Desbrun-Kanso-Tong 2006, Soliman et al. 2018,
all Bobenko-Lutz papers, Lutz 2023/2024, Bowers-Bowers-Lutz 2026,
Alexa-Wardetzky 2011, Bunge et al. 2020, de Goes et al. 2020,
Gillespie-Springborn-Crane 2021, Sharp-Soliman-Crane 2019, Farkas-Kra,
Siegel, Bobenko-Bücking 2021, Rivin-Schlenker 1999, Pinkall-Springborn 2021,
Sawhney-Crane 2017

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

doc/math/references.md

@@ -31,9 +31,9 @@ Java reference implementation: [github.com/varylab/conformallab](https://github.
 | ✅ **Springborn** — *Ideal Hyperbolic Polyhedra and Discrete Uniformization*, Discrete & Computational Geometry **64** (2020), pp. 63–108. DOI: [10.1007/s00454-019-00132-8](https://doi.org/10.1007/s00454-019-00132-8) | `hyper_ideal_geometry.hpp` — ζ₁₃/ζ₁₄/ζ₁₅ functions; `hyper_ideal_functional.hpp` |
 | ✅ **Springborn** — *A variational principle for weighted Delaunay triangulations and hyperideal polyhedra*, J. Differential Geometry **78**(2) (2008), pp. 333–367. arXiv: [math/0603097](https://arxiv.org/abs/math/0603097) | Tetrahedron volume with one ideal vertex: `calculateTetrahedronVolumeWithIdealVertexAtGamma` in `hyper_ideal_utility.hpp` (Phase 9b analytic Hessian). ⚠️ *Korrektur:* war fälschlich als „Kolpakov–Mednykh 2006" zitiert — dieses Autorenpaar hat 2006 kein gemeinsames Paper veröffentlicht. Die Java-Quelle verlinkt korrekt auf math/0603097 (= Springborn 2008); der falsche Autorenname wurde beim C++-Port hinzugefügt.* |
 | ✅ **Ushijima** — *A Volume Formula for Generalised Hyperbolic Tetrahedra*, in: Prékopa, Molnár (eds.) *Non-Euclidean Geometries*, Mathematics and Its Applications vol. 581, Springer 2006. DOI: [10.1007/0-387-29555-0_13](https://doi.org/10.1007/0-387-29555-0_13). arXiv: [math/0309216](https://arxiv.org/abs/math/0309216) (2003) | Tetrahedron volume with three ideal vertices: `calculateTetrahedronVolumeFullyIdeal` in `hyper_ideal_utility.hpp`. ⚠️ *Korrektur:* war fälschlich als „Meyerhoff, Ushijima — A Note on the Dirichlet Domain — The Epstein Birthday Schrift" zitiert. Meyerhoff ist kein Autor; Titel und Buch waren beide falsch. Die Java-Quelle verlinkt korrekt auf DOI 10.1007/0-387-29555-0_13 ohne Autorennamen. |
-| **Pinkall, Polthier** — *Computing Discrete Minimal Surfaces and Their Conjugates*, Experimental Mathematics (1993) | `euclidean_hessian.hpp` — cotangent Laplacian |
+| **Pinkall, Polthier** — *Computing Discrete Minimal Surfaces and Their Conjugates*, Experimental Mathematics **2**(1), pp. 15–36 (1993). DOI: [10.1080/10586458.1993.10504266](https://doi.org/10.1080/10586458.1993.10504266) | `euclidean_hessian.hpp` — cotangent Laplacian |
-| **Bobenko, Springborn** — *Variational Principles for Circle Patterns and Koebe's Theorem*, Transactions AMS (2004) | Variational angle-sum framework underlying all three functionals |
+| **Bobenko, Springborn** — *Variational Principles for Circle Patterns and Koebe's Theorem*, Trans. Amer. Math. Soc. **356**(2), pp. 659–689 (2004). arXiv: [math/0203250](https://arxiv.org/abs/math/0203250) | Variational angle-sum framework underlying all three functionals |
-| **Luo** — *Combinatorial Yamabe Flow on Surfaces*, Communications in Contemporary Mathematics (2004) | Inversive-distance functional — **new research** in Phase 9a.2 (no Java original; implemented from this paper + Glickenstein 2011 + Bowers-Stephenson 2004) |
+| **Luo** — *Combinatorial Yamabe Flow on Surfaces*, Commun. Contemp. Math. **6**(5), pp. 765–780 (2004). DOI: [10.1142/S0219199704001501](https://doi.org/10.1142/S0219199704001501). arXiv: [math/0306167](https://arxiv.org/abs/math/0306167) | Inversive-distance functional — **new research** in Phase 9a.2 (no Java original; implemented from this paper + Glickenstein 2011 + Bowers-Stephenson 2004) |
 | **Bowers, Stephenson** — *Uniformizing dessins and Belyĭ maps via circle packing*, Memoirs of the AMS 170(805) (2004) | Introduces **inversive-distance circle packings** (used in Phase 9a.2). *Hinweis:* die zur Initialisierung benutzte Formel I_ij = (ℓ²−r_i²−r_j²)/(2 r_i r_j) ist die **klassische** inversive Distanz (vgl. Glickenstein §5.2: ℓ²=r_i²+r_j²+2r_ir_jη), nicht eine eigene „Bowers-Stephenson-Identität" — B–S liefern die Packungstheorie, nicht diese Formel. |
 | **Glickenstein** — *Discrete conformal variations and scalar curvature on piecewise flat two- and three-dimensional manifolds*, J. Differential Geometry **87**(2) (2011), pp. 201–238 | Analytic Hessian of the inversive-distance functional. ⚠️ *Korrektur:* die Arbeit nummeriert Gleichungen **nicht** im Format „(4.6)" — der Verweis ist durch die **§5.2**-Parametrisierung ℓ²_ij = r²_i + r²_j + 2 r_i r_j η_ij zu ersetzen. Cross-correspondence: η_ij ist die inversive Distanz und entspricht dem Kosinus des **Supplements** des Schnittwinkels (Schnitt bei arccos(−η_ij)) — also I_ij = cos θ_e **nur bis aufs Vorzeichen/Supplement**, nicht wörtlich. |
 | ✅ **Bobenko, Pinkall, Springborn** — *Discrete conformal maps and ideal hyperbolic polyhedra*, Geometry & Topology **19**(4) (2015), pp. 2155–2215. arXiv: [1005.2698](https://arxiv.org/abs/1005.2698) (first posted 2010) | Face-based circle-packing functional (`CPEuclideanFunctional.java` → `cp_euclidean_functional.hpp`, Phase 9a.1) |
@@ -79,10 +79,10 @@ builds on this paper and augments it with Ptolemaic flips.
 |---|---|
 | **Farkas, Kra** — *Riemann Surfaces*, Springer GTM 71 | Siegel period matrix, Teichmüller theory |
 | **Siegel** — *Topics in Complex Function Theory, Vol. 2*, Wiley | Siegel upper half-space H_g, Sp(2g,ℤ) reduction |
-| **Bobenko, Mercat, Schmies** — *Period Matrices of Polyhedral Surfaces*, in: Computational Approach to Riemann Surfaces (2011) | Discrete period matrices on polyhedral surfaces |
+| **Bobenko, Mercat, Schmies** — *Conformal Structures and Period Matrices of Polyhedral Surfaces*, in: Bobenko, Klein (eds.) *Computational Approach to Riemann Surfaces*, Lecture Notes in Mathematics vol. 2013, Springer 2011, pp. 213–226. DOI: [10.1007/978-3-642-17413-1_7](https://doi.org/10.1007/978-3-642-17413-1_7) | Discrete period matrices on polyhedral surfaces |
 | **Bobenko, Bücking** — *Convergence of discrete period matrices and discrete holomorphic integrals for ramified coverings of the Riemann sphere*, Math. Phys. Anal. Geom. **24**, Art. 23 (2021). DOI: [10.1007/s11040-021-09394-2](https://doi.org/10.1007/s11040-021-09394-2) | Phase 10b: discrete Siegel period matrix Ωᵢⱼ from cotangent-weighted integration **plus** the convergence result Ω_discrete → Ω_smooth under refinement (für ramified coverings) — belegt die Diskret-zu-glatt-Aussage in `novelty-statement.md §3.3. |
 | **Rivin, Schlenker** — *The Schläfli formula in Einstein manifolds with boundary*, Electron. Res. Announc. AMS **5** (1999), pp. 18–23 | Phase 9b-analytic: modern form of the Schläfli identity `2 dV = Σ aₑ dαₑ` for manifolds with boundary — the bilinear form used to derive the analytic HyperIdeal Hessian. |
 | **Pinkall, Springborn** — *A discrete version of Liouville's theorem on conformal maps*, Geometriae Dedicata **214** (2021), pp. 389–398. arXiv: [1911.00966](https://arxiv.org/abs/1911.00966) | Phase 10b uniqueness: proves that the discrete conformal structure (and hence Ω) is a conformal invariant — the discrete Liouville theorem. Justifies that conformallab++ outputs a canonical representative. |
-| **Born, Bücking, Springborn** — *Quasiconformal distortion of projective transformations and discrete conformal maps*, arXiv: [1505.01341](https://arxiv.org/abs/1505.01341) (2015) | Phase 10c error analysis: quantifies how well the discrete H²/Γ embedding approximates the smooth hyperbolic metric; error bounds for the Fuchsian group representation. |
+| **Born, Bücking, Springborn** — *Quasiconformal distortion of projective transformations and discrete conformal maps*, Discrete & Computational Geometry **57**(2), pp. 305–317 (2017). DOI: [10.1007/s00454-016-9854-7](https://doi.org/10.1007/s00454-016-9854-7). arXiv: [1505.01341](https://arxiv.org/abs/1505.01341) (preprint 2015) | Phase 10c error analysis: quantifies how well the discrete H²/Γ embedding approximates the smooth hyperbolic metric; error bounds for the Fuchsian group representation. |
-| **Knöppel, Crane, Pinkall, Schröder** — *Stripe Patterns on Surfaces*, ACM SIGGRAPH (2015). DOI: [10.1145/2766890](https://doi.org/10.1145/2766890) | Phase 10a cross-validation: applies discrete holomorphic 1-forms to direction field design; geometry-central provides an independent C++ implementation to cross-check the Phase 10a `DiscreteHolomorphicFormUtility` port. |
+| **Knöppel, Crane, Pinkall, Schröder** — *Stripe Patterns on Surfaces*, ACM Transactions on Graphics **34**(4), Article 39 (SIGGRAPH 2015). DOI: [10.1145/2767000](https://doi.org/10.1145/2767000). ⚠️ *Kein arXiv-Preprint* (arXiv:1502.06686 ist ein anderes Paper — Data-Driven Shape Analysis — und wurde aus dem papers/-Ordner entfernt). | Phase 10a cross-validation: applies discrete holomorphic 1-forms to direction field design; geometry-central provides an independent C++ implementation to cross-check the Phase 10a `DiscreteHolomorphicFormUtility` port. |
 | **Sawhney, Crane** — *Boundary First Flattening*, ACM TOG **37**(1), Article 5 (2017). DOI: [10.1145/3132705](https://doi.org/10.1145/3132705) | Complementary method to Phase 9d: boundary-prescribed conformal flattening — user specifies boundary shape, interior conforms freely. Contrast: conformallab++ prescribes cone angles in the interior; BFF prescribes the boundary. Alternative approach for applications needing controlled boundary. |