Langer, H.; de Snoo, H. S. V.; Yavrian, V. A. A relation for the spectral shift function of two self-adjoint extensions. (English) Zbl 0999.47022 Kérchy, László (ed.) et al., Recent advances in operator theory and related topics. The Béla Szőkefalvi-Nagy memorial volume. Proceedings of the memorial conference, Szeged, Hungary, August 2-6, 1999. Basel: Birkhäuser. Oper. Theory, Adv. Appl. 127, 437-445 (2001). Reviewer: J.B.Butler jun.(Portland) MSC: 47B25 47A20 47A55 34B20 47A10 47B10 PDFBibTeX XMLCite \textit{H. Langer} et al., in: Recent advances in operator theory and related topics. The Béla Szőkefalvi-Nagy memorial volume. Proceedings of the memorial conference, Szeged, Hungary, August 2--6, 1999. Basel: Birkhäuser. 437--445 (2001; Zbl 0999.47022)
Langer, Heinz; Luger, Annemarie A class of \(2\times 2\)-matrix functions. (English) Zbl 1006.47033 Glas. Mat., III. Ser. 35, No. 1, 149-160 (2000). Reviewer: Trandafir Balan (Craiova) MSC: 47B50 47A56 30E99 PDFBibTeX XMLCite \textit{H. Langer} and \textit{A. Luger}, Glas. Mat., III. Ser. 35, No. 1, 149--160 (2000; Zbl 1006.47033)
Curgus, Branko; Gheondea, Aurelian; Langer, Heinz On singular critical points of positive operators in Krein spaces. (English) Zbl 0952.47033 Proc. Am. Math. Soc. 128, No. 9, 2621-2626 (2000). Reviewer: A.Duma (Hagen) MSC: 47B50 46C20 PDFBibTeX XMLCite \textit{B. Curgus} et al., Proc. Am. Math. Soc. 128, No. 9, 2621--2626 (2000; Zbl 0952.47033) Full Text: DOI
Langer, H.; Najman, B. Instability of singular critical points of definitizable operators. (English) Zbl 0897.47031 Integral Equations Oper. Theory 28, No. 1, 60-71 (1997). MSC: 47B50 47A55 PDFBibTeX XMLCite \textit{H. Langer} and \textit{B. Najman}, Integral Equations Oper. Theory 28, No. 1, 60--71 (1997; Zbl 0897.47031) Full Text: DOI
Jonas, Peter; Langer, Heinz Selfadjoint extensions of a closed linear relation of defect one in a Krein space. (English) Zbl 0846.47025 Gohberg, I. (ed.) et al., Operator theory and boundary eigenvalue problems. Proceedings of the international workshop held in Vienna, Austria, July 27-30, 1993. Basel: Birkhäuser. Oper. Theory, Adv. Appl. 80, 176-205 (1995). MSC: 47B50 47A20 PDFBibTeX XMLCite \textit{P. Jonas} and \textit{H. Langer}, in: Operator theory and boundary eigenvalue problems. Proceedings of the international workshop held in Vienna, Austria, July 27-30, 1993. Basel: Birkhäuser. 176--205 (1995; Zbl 0846.47025)
Jonas, P.; Langer, H.; Textorius, B. Models and unitary equivalence of cyclic selfadjoint operators in Pontrjagin spaces. (English) Zbl 0794.47022 Ando, T. (ed.) et al., Operator theory and complex analysis. Proceedings of a workshop, held in Sapporo, Japan, June 11-14, 1991. Basel: Birkhäuser. Oper. Theory, Adv. Appl. 59, 252-284 (1992). MSC: 47B50 47A67 47A45 PDFBibTeX XMLCite \textit{P. Jonas} et al., in: Operator theory and complex analysis. Proceedings of a workshop, held in Sapporo, Japan, June 11-14, 1991. Basel: Birkhäuser. 252--284 (1992; Zbl 0794.47022)
Dijksma, Aad; Langer, Heinz; de Snoo, Henk Generalized coresolvents of standard isometric operators and generalized resolvents of standard symmetric relations in Krejn spaces. (English) Zbl 0734.47018 Topics in operator theory. Ernst D. Hellinger Mem. Vol., Oper. Theory, Adv. Appl. 48, 261-274 (1990). MSC: 47B50 47A48 47A10 47A56 47A20 PDFBibTeX XML
Langer, H.; Mennicken, R.; Möller, M. A second order differential operator depending nonlinearly on the eigenvalue parameter. (English) Zbl 0734.34070 Topics in operator theory. Ernst D. Hellinger Mem. Vol., Oper. Theory, Adv. Appl. 48, 319-332 (1990). Reviewer: G.Moroşanu (Iaşi) MSC: 34L05 PDFBibTeX XML
Ćurgus, B.; Dijksma, A.; Langer, H.; de Snoo, H. S. V. Characteristic functions of unitary colligations and of bounded operators in Krein spaces. (English) Zbl 0674.47024 Oper. Theory, Adv. Appl. 41, 125-152 (1989). Reviewer: T.Ando MSC: 47B50 47A56 47A45 PDFBibTeX XML
Dijksma, A.; Langer, H.; de Snoo, H. S. V. Unitary colligations in \(\pi _ k\)-spaces, characteristic functions and Shtraus extensions. (English) Zbl 0573.47027 Pac. J. Math. 125, 347-362 (1986). MSC: 47B50 47D99 PDFBibTeX XMLCite \textit{A. Dijksma} et al., Pac. J. Math. 125, 347--362 (1986; Zbl 0573.47027) Full Text: DOI
Iohvidov, I. S.; Krein, M. G.; Langer, H. Introduction to the spectral theory of operators in spaces with an indefinite metric. (English) Zbl 0506.47022 Mathematical Research, Vol. 9. Berlin: Akademie-Verlag. 120 p. M 15.00 (1982). MSC: 47B50 47-02 46C20 PDFBibTeX XML
Kreijn, Mark Grigor’evich; Langer, Heinz On some extension problems which are closely connected with the theory of hermitian operators in a space \(\Pi_ \kappa\). III: Indefinite analogues of the Hamburger and Stieltjes moment problem. II. (English) Zbl 0507.47022 Beitr. Anal. 15, 27-45 (1981). MSC: 47B50 46C20 PDFBibTeX XMLCite \textit{M. G. Kreijn} and \textit{H. Langer}, Beitr. Anal. 15, 27--45 (1981; Zbl 0507.47022)
Kreijn, Mark Grigor’evich; Langer, Heinz On some extension problems which are closely connected with the theory of hermitian operators in a space \(\Pi_ \kappa\). III: Indefinite analogues of the Hamburger and Stieltjes moment problems. I. (English) Zbl 0507.47021 Beitr. Anal. 14, 25-40 (1979). MSC: 47B50 46C20 PDFBibTeX XMLCite \textit{M. G. Kreijn} and \textit{H. Langer}, Beitr. Anal. 14, 25--40 (1979; Zbl 0507.47021)