Prajapati, Pawan; Singh, Gyanvendra Pratap; Rajan; Mishra, Anand Kumar A study of \(W_8\)-curvature tensor in Lorentzian \(\beta\)-Kenmotsu manifold. (English) Zbl 07787646 J. Rajasthan Acad. Phys. Sci. 22, No. 3-4, 225-236 (2023). MSC: 53C05 53C20 53C25 53D15 PDFBibTeX XMLCite \textit{P. Prajapati} et al., J. Rajasthan Acad. Phys. Sci. 22, No. 3--4, 225--236 (2023; Zbl 07787646) Full Text: Link
Amruthalakshmi, M. R.; Prakasha, D. G.; Turki, Nasser Bin; Unal, Inan \(\ast\)-Ricci tensor on \(\alpha\)-cosymplectic manifolds. (English) Zbl 1493.53037 Adv. Math. Phys. 2022, Article ID 7939654, 11 p. (2022). MSC: 53C15 53C25 53D05 PDFBibTeX XMLCite \textit{M. R. Amruthalakshmi} et al., Adv. Math. Phys. 2022, Article ID 7939654, 11 p. (2022; Zbl 1493.53037) Full Text: DOI
Bulut, Şenay A semi-symmetric metric connection on almost contact \(B\)-metric manifolds. (English) Zbl 1501.53022 Turk. J. Math. 45, No. 6, 2455-2465 (2021). Reviewer: María Ferreiro-Subrido (Santiago de Compostela) MSC: 53C05 53C15 53D15 PDFBibTeX XMLCite \textit{Ş. Bulut}, Turk. J. Math. 45, No. 6, 2455--2465 (2021; Zbl 1501.53022) Full Text: DOI
Prasad, Rajendra; Haseeb, Abdul; Gautam, Umesh Kumar On \(\check\phi\)-semisymmetric LP-Kenmotsu manifolds with a QSNM-connection admitting Ricci solitons. (English) Zbl 1499.53322 Kragujevac J. Math. 45, No. 5, 815-827 (2021). MSC: 53D15 53C05 53C25 PDFBibTeX XMLCite \textit{R. Prasad} et al., Kragujevac J. Math. 45, No. 5, 815--827 (2021; Zbl 1499.53322) Full Text: DOI Link
Ghosh, Gopal; De, Uday Chand On almost Kenmotsu manifolds with generalized nullity distribution. (English) Zbl 1498.53103 Acta Math. Univ. Comen., New Ser. 89, No. 2, 309-317 (2020). MSC: 53D15 PDFBibTeX XMLCite \textit{G. Ghosh} and \textit{U. C. De}, Acta Math. Univ. Comen., New Ser. 89, No. 2, 309--317 (2020; Zbl 1498.53103) Full Text: Link
De, Uday Chand; Zhao, Peibiao; Mandal, Krishanu; Han, Yanling Certain curvature conditions on \(P\)-Sasakian manifolds admitting a quater-symmetric metric connection. (English) Zbl 1432.53041 Chin. Ann. Math., Ser. B 41, No. 1, 133-146 (2020). MSC: 53C15 PDFBibTeX XMLCite \textit{U. C. De} et al., Chin. Ann. Math., Ser. B 41, No. 1, 133--146 (2020; Zbl 1432.53041) Full Text: DOI
Shaikh, Absos Ali; Mondal, Chandan Kumar; Ahmad, Helaluddin On locally \(\phi\)-semisymmetric Sasakian manifolds. (English) Zbl 1488.53115 Hacet. J. Math. Stat. 48, No. 4, 1156-1169 (2019). MSC: 53C15 53C25 PDFBibTeX XMLCite \textit{A. A. Shaikh} et al., Hacet. J. Math. Stat. 48, No. 4, 1156--1169 (2019; Zbl 1488.53115) Full Text: Link
Mandal, Krishanu; De, Uday Chand Paracontact metric \((k,\mu)\)-spaces satisfying certain curvature conditions. (English) Zbl 1433.53043 Kyungpook Math. J. 59, No. 1, 163-174 (2019). MSC: 53C15 53B30 53C25 53D10 53D15 PDFBibTeX XMLCite \textit{K. Mandal} and \textit{U. C. De}, Kyungpook Math. J. 59, No. 1, 163--174 (2019; Zbl 1433.53043) Full Text: DOI
Chaubey, Sudhakar K.; Yildiz, Ahmet Riemannian manifolds admitting a new type of semisymmetric nonmetric connection. (English) Zbl 1433.53026 Turk. J. Math. 43, No. 4, 1887-1904 (2019). MSC: 53B20 53B05 PDFBibTeX XMLCite \textit{S. K. Chaubey} and \textit{A. Yildiz}, Turk. J. Math. 43, No. 4, 1887--1904 (2019; Zbl 1433.53026) Full Text: Link
Barman, Ajit On para-Sasakian manifolds admitting a special type of semi-symmetric non-metric \(\eta\)-connection. (English) Zbl 1417.53029 Palest. J. Math. 8, No. 2, 266-274 (2019). MSC: 53C15 53C25 PDFBibTeX XMLCite \textit{A. Barman}, Palest. J. Math. 8, No. 2, 266--274 (2019; Zbl 1417.53029) Full Text: Link
Majhi, Pradip; Ghosh, Gopal Certain results on generalized \((k,\mu)\)-contact manifolds. (English) Zbl 1424.53067 Bol. Soc. Parana. Mat. (3) 37, No. 3, 131-142 (2019). MSC: 53C15 53C25 PDFBibTeX XMLCite \textit{P. Majhi} and \textit{G. Ghosh}, Bol. Soc. Parana. Mat. (3) 37, No. 3, 131--142 (2019; Zbl 1424.53067) Full Text: Link
Zhao, Peibiao; De, Uday Chand; Mandal, Krishanu; Han, Yanling Certain curvature conditions on Kenmotsu manifolds admitting a quarter-symmetric metric connection. (English) Zbl 1499.53123 Publ. Inst. Math., Nouv. Sér. 104(118), 169-181 (2018). MSC: 53C05 53D15 53C15 PDFBibTeX XMLCite \textit{P. Zhao} et al., Publ. Inst. Math., Nouv. Sér. 104(118), 169--181 (2018; Zbl 1499.53123) Full Text: DOI
Arasaiah; Venkatesha Almost Kenmotsu manifold equipped with \(M\)-projective curvature tensor. (English) Zbl 1478.53082 J. Tensor Soc. (N.S.) 12, 73-83 (2018). MSC: 53C25 53D15 PDFBibTeX XMLCite \textit{Arasaiah} and \textit{Venkatesha}, J. Tensor Soc. (N.S.) 12, 73--83 (2018; Zbl 1478.53082) Full Text: Link
Deshmukh, Sharief; De, Uday Chand; Zhao, Peibiao Ricci semisymmetric almost Kenmotsu manifolds with nullity distributions. (English) Zbl 1488.53154 Filomat 32, No. 1, 179-186 (2018). MSC: 53C25 53C35 PDFBibTeX XMLCite \textit{S. Deshmukh} et al., Filomat 32, No. 1, 179--186 (2018; Zbl 1488.53154) Full Text: DOI
Paul, Avijit Kumar Some curvature properties of \(S\)-manifolds. (English) Zbl 1418.53035 J. Indian Acad. Math. 40, No. 1, 121-131 (2018). MSC: 53C15 53C25 PDFBibTeX XMLCite \textit{A. K. Paul}, J. Indian Acad. Math. 40, No. 1, 121--131 (2018; Zbl 1418.53035)
Turgut Vanli, Aysel; Unal, Inan \(H\)-curvature tensors on IK-normal complex contact metric manifolds. (English) Zbl 1405.53046 Int. J. Geom. Methods Mod. Phys. 15, No. 12, Article ID 1850205, 13 p. (2018). MSC: 53C15 53C25 53D10 70G45 PDFBibTeX XMLCite \textit{A. Turgut Vanli} and \textit{I. Unal}, Int. J. Geom. Methods Mod. Phys. 15, No. 12, Article ID 1850205, 13 p. (2018; Zbl 1405.53046) Full Text: DOI
Ghosh, Gopal; Majhi, Pradip Certain results on almost Kenmotsu manifolds with conformal Reeb foliation. (English) Zbl 1395.53026 Commun. Korean Math. Soc. 33, No. 1, 261-272 (2018). MSC: 53C15 53C25 PDFBibTeX XMLCite \textit{G. Ghosh} and \textit{P. Majhi}, Commun. Korean Math. Soc. 33, No. 1, 261--272 (2018; Zbl 1395.53026) Full Text: DOI
Mandal, Krishanu; De, Uday Chand Some curvature properties of paracontact metric manifolds. (English) Zbl 1395.53030 Adv. Pure Appl. Math. 9, No. 3, 159-165 (2018). Reviewer: Corina Mohorianu (Iaşi) MSC: 53C15 53B30 53C25 53D10 53D15 PDFBibTeX XMLCite \textit{K. Mandal} and \textit{U. C. De}, Adv. Pure Appl. Math. 9, No. 3, 159--165 (2018; Zbl 1395.53030) Full Text: DOI
Majhi, Pradip; De, Uday Chand Classification of Ricci semisymmetric contact metric manifolds. (English) Zbl 1488.53106 Filomat 31, No. 8, 2527-2535 (2017). MSC: 53C15 53C25 PDFBibTeX XMLCite \textit{P. Majhi} and \textit{U. C. De}, Filomat 31, No. 8, 2527--2535 (2017; Zbl 1488.53106) Full Text: DOI
Yıldız, Ahmet \(f\)-Kenmotsu manifolds with the Schouten-van Kampen connection. (English) Zbl 1474.53188 Publ. Inst. Math., Nouv. Sér. 102(116), 93-105 (2017). MSC: 53C15 53C25 53C50 PDFBibTeX XMLCite \textit{A. Yıldız}, Publ. Inst. Math., Nouv. Sér. 102(116), 93--105 (2017; Zbl 1474.53188) Full Text: DOI
De, Uday Chand; Deshmukh, Sharief; Mandal, Krishanu On three-dimensional \(N(k)\)-paracontact metric manifolds and Ricci solitons. (English) Zbl 1406.53029 Bull. Iran. Math. Soc. 43, No. 6, 1571-1583 (2017). MSC: 53C15 53C25 PDFBibTeX XMLCite \textit{U. C. De} et al., Bull. Iran. Math. Soc. 43, No. 6, 1571--1583 (2017; Zbl 1406.53029) Full Text: Link
Prakasha, D. G.; Hadimani, B. S. \(\eta\)-Ricci solitons on para-Sasakian manifolds. (English) Zbl 1376.53057 J. Geom. 108, No. 2, 383-392 (2017). MSC: 53C15 53C44 PDFBibTeX XMLCite \textit{D. G. Prakasha} and \textit{B. S. Hadimani}, J. Geom. 108, No. 2, 383--392 (2017; Zbl 1376.53057) Full Text: DOI
Mandal, K.; De, U. C. On 3-dimensional almost Kenmotsu manifolds admitting certain nullity distribution. (English) Zbl 1399.53081 Acta Math. Univ. Comen., New Ser. 86, No. 2, 215-226 (2017). Reviewer: Yaning Wang (Guangdong) MSC: 53C25 PDFBibTeX XMLCite \textit{K. Mandal} and \textit{U. C. De}, Acta Math. Univ. Comen., New Ser. 86, No. 2, 215--226 (2017; Zbl 1399.53081)
Barman, A. On \(N(k)\)-contact metric manifolds admitting a type of a semi-symmetric non-metric connection. (English) Zbl 1374.53049 Acta Math. Univ. Comen., New Ser. 86, No. 1, 81-90 (2017). Reviewer: Giovanni Calvaruso (Lecce) MSC: 53C15 PDFBibTeX XMLCite \textit{A. Barman}, Acta Math. Univ. Comen., New Ser. 86, No. 1, 81--90 (2017; Zbl 1374.53049)
Doğru, Yusuf Hypersurfaces satisfying some curvature conditions on quasi-conformal curvature tensor in the semi-euclidean space. (English) Zbl 1389.53008 An. Științ. Univ. Al. I. Cuza Iași, Ser. Nouă, Mat. 62, No. 2, Part 2, 695-703 (2016). MSC: 53A05 53A10 53B20 53C20 PDFBibTeX XMLCite \textit{Y. Doğru}, An. Științ. Univ. Al. I. Cuza Iași, Ser. Nouă, Mat. 62, No. 2, Part 2, 695--703 (2016; Zbl 1389.53008)
Ghosh, Gopal; De, Uday Chand On a semi-symmetric metric connection in an almost Kenmotsu manifold with nullity distributions. (English) Zbl 1372.53048 Acta Univ. Palacki. Olomuc., Fac. Rerum Nat., Math. 55, No. 2, 87-99 (2016). Reviewer: Radu Iordănescu (Bucureşti) MSC: 53C25 53C35 53C15 PDFBibTeX XMLCite \textit{G. Ghosh} and \textit{U. C. De}, Acta Univ. Palacki. Olomuc., Fac. Rerum Nat., Math. 55, No. 2, 87--99 (2016; Zbl 1372.53048) Full Text: Link
Dey, Santu; Pal, Buddhadev; Bhattacharyya, Arindam On some classes of mixed-super quasi-Einstein manifolds. (English) Zbl 1345.53041 Acta Univ. Sapientiae, Math. 8, No. 1, 32-52 (2016). MSC: 53C25 53B30 PDFBibTeX XMLCite \textit{S. Dey} et al., Acta Univ. Sapientiae, Math. 8, No. 1, 32--52 (2016; Zbl 1345.53041) Full Text: DOI
Suthar, D. L.; Yadav, S. K. Some curvature properties of a Lorentzian concircular structure manifolds. (English) Zbl 1359.53024 Proceedings of the national conference on advances in mathematical sciences and applications in engineering and technology, AMS-AET, July 25–26, 2015. Rajasthan: Rajasthan Academy of Physical Sciences (RAOPS). 87-100 (2015). MSC: 53C15 53C05 53C10 53D15 PDFBibTeX XMLCite \textit{D. L. Suthar} and \textit{S. K. Yadav}, in: Proceedings of the national conference on advances in mathematical sciences and applications in engineering and technology, AMS-AET, July 25--26, 2015. Rajasthan: Rajasthan Academy of Physical Sciences (RAOPS). 87--100 (2015; Zbl 1359.53024)
Chand De, Uday; Yildiz, Ahmet; Çetinkaya, Azime Certain results on a type of contact metric manifold. (English) Zbl 1329.53044 Afr. Mat. 26, No. 7-8, 1229-1236 (2015). MSC: 53C15 53C25 PDFBibTeX XMLCite \textit{U. Chand De} et al., Afr. Mat. 26, No. 7--8, 1229--1236 (2015; Zbl 1329.53044) Full Text: DOI
Doğru, Yusuf Hypersurfaces satisfying some curvature conditions on pseudo projective curvature tensor in the semi-Euclidean space. (English) Zbl 1439.53020 Math. Sci. Appl. E-Notes 2, No. 1, 99-105 (2014). MSC: 53B20 53C25 53B30 53C40 PDFBibTeX XMLCite \textit{Y. Doğru}, Math. Sci. Appl. E-Notes 2, No. 1, 99--105 (2014; Zbl 1439.53020)
Kim, Jaeman Some properties of \(N(k)\)-quasi Einstein manifolds. (English) Zbl 1322.53035 Int. J. Pure Appl. Math. 88, No. 3, 351-362 (2013). MSC: 53C15 53C25 53B20 PDFBibTeX XMLCite \textit{J. Kim}, Int. J. Pure Appl. Math. 88, No. 3, 351--362 (2013; Zbl 1322.53035) Full Text: DOI Link
Doğru, Y.; Özgür, C.; Murathan, C. Riemannian manifolds with a semi-symmetric non-metric connection satisfying some semisymmetry conditions. (English) Zbl 1314.53051 Bull. Math. Anal. Appl. 3, No. 2, 206-212 (2011). MSC: 53C05 53B15 PDFBibTeX XMLCite \textit{Y. Doğru} et al., Bull. Math. Anal. Appl. 3, No. 2, 206--212 (2011; Zbl 1314.53051) Full Text: Link
Prakash, Amit; Narain, Dhruwa On a class of Lorentzian para-Sasakian manifolds. (English) Zbl 1223.53026 Bull. Pure Appl. Math. 4, No. 2, 297-308 (2010). MSC: 53C15 PDFBibTeX XMLCite \textit{A. Prakash} and \textit{D. Narain}, Bull. Pure Appl. Math. 4, No. 2, 297--308 (2010; Zbl 1223.53026)
Shaikh, Absos Ali; Hui, Shyamal Kumar On some classes of generalized quasi-Einstein manifolds. (English) Zbl 1231.53041 Commun. Korean Math. Soc. 24, No. 3, 415-424 (2009). MSC: 53C25 PDFBibTeX XMLCite \textit{A. A. Shaikh} and \textit{S. K. Hui}, Commun. Korean Math. Soc. 24, No. 3, 415--424 (2009; Zbl 1231.53041) Full Text: DOI
Özgür, Cihan; Tripathi, Mukut Mani On submanifolds satisfying Chen’s equality in a real space form. (English) Zbl 1185.53060 Arab. J. Sci. Eng., Sect. A, Sci. 33, No. 2, 321-330 (2008). MSC: 53C40 53C25 53C42 PDFBibTeX XMLCite \textit{C. Özgür} and \textit{M. M. Tripathi}, Arab. J. Sci. Eng., Sect. A, Sci. 33, No. 2, 321--330 (2008; Zbl 1185.53060)
Tripathi, Mukut Mani Classification of \(\xi\)-Ricci-semisymmetric \((\kappa,\mu)\)-manifolds. (English) Zbl 1109.53049 Balkan J. Geom. Appl. 11, No. 2, 134-142 (2006). MSC: 53C25 53D10 PDFBibTeX XMLCite \textit{M. M. Tripathi}, Balkan J. Geom. Appl. 11, No. 2, 134--142 (2006; Zbl 1109.53049) Full Text: EuDML
Jun, Jae-Bok; De, Uday Chand; Pathak, Goutam On Kenmotsu manifolds. (English) Zbl 1075.53040 J. Korean Math. Soc. 42, No. 3, 435-445 (2005). Reviewer: Marian Hotloś (Wrocław) MSC: 53C25 PDFBibTeX XMLCite \textit{J.-B. Jun} et al., J. Korean Math. Soc. 42, No. 3, 435--445 (2005; Zbl 1075.53040) Full Text: DOI
Ṡentürk, Zerrin Pseudosymmetry type curvature conditions. (English) Zbl 1070.53006 Andrica, Dorin (ed.) et al., Recent advances in geometry and topology. Proceedings of the 6th international workshop on differential geometry and its applications and the 3rd German-Romanian seminar on geometry, Cluj-Napoca, Romania, September 1–6, 2003. Cluj-Napoca: Cluj University Press (ISBN 973-610-277-7/hbk). 363-366 (2004). Reviewer: Hans-Jürgen Schmidt (Potsdam) MSC: 53B20 53B30 53C15 53B50 PDFBibTeX XMLCite \textit{Z. Ṡentürk}, in: Recent advances in geometry and topology. Proceedings of the 6th international workshop on differential geometry and its applications and the 3rd German-Romanian seminar on geometry, Cluj-Napoca, Romania, September 1--6, 2003. Cluj-Napoca: Cluj University Press. 363--366 (2004; Zbl 1070.53006)
De, U. C.; Sengupta, Anup Kumar Notes on three-dimensional quasi-Sasakian manifolds. (English) Zbl 1086.53045 Demonstr. Math. 37, No. 3, 655-660 (2004). Reviewer: Valentin Boju (Montreal) MSC: 53C15 PDFBibTeX XMLCite \textit{U. C. De} and \textit{A. K. Sengupta}, Demonstr. Math. 37, No. 3, 655--660 (2004; Zbl 1086.53045) Full Text: DOI
Deszcz, Ryszard; Głogowska, Małgorzata Some nonsemisymmetric Ricci-semisymmetric warped product hypersurfaces. (English) Zbl 1060.53024 Publ. Inst. Math., Nouv. Sér. 72(86), 81-93 (2002). Reviewer: Miroslava Torgašev-Petrović (Kragujevac) MSC: 53B30 53B20 53B50 53C25 PDFBibTeX XMLCite \textit{R. Deszcz} and \textit{M. Głogowska}, Publ. Inst. Math., Nouv. Sér. 72(86), 81--93 (2002; Zbl 1060.53024) Full Text: DOI
Deszcz, Ryszard; Głogowska, Małgorzata Examples of nonsemisymmetric Ricci-semisymmetric hypersurfaces. (English) Zbl 1026.53010 Colloq. Math. 94, No. 1, 87-101 (2002). Reviewer: Lew Friedland (Geneseo) MSC: 53B30 53B25 53C40 53C35 53B50 53B20 PDFBibTeX XMLCite \textit{R. Deszcz} and \textit{M. Głogowska}, Colloq. Math. 94, No. 1, 87--101 (2002; Zbl 1026.53010) Full Text: DOI
Murathan, Cengizhan; Arslan, Kadri; Deszcz, Ryszard; Ezentaṣ, Ridvan; Özgür, Cihan On some class of hypersurfaces of semi-Euclidean spaces. (English) Zbl 1012.53017 Publ. Math. Debr. 58, No. 4, 587-604 (2001). Reviewer: Péter T.Nagy (Debrecen) MSC: 53B20 53B25 53B50 PDFBibTeX XMLCite \textit{C. Murathan} et al., Publ. Math. Debr. 58, No. 4, 587--604 (2001; Zbl 1012.53017)
Deszcz, Ryszard; Hotloś, Marian; Ṣentürk, Zerrin Quasi-Einstein hypersurfaces in semi-Riemannian space forms. (English) Zbl 0991.53009 Colloq. Math. 89, No. 1, 81-97 (2001). Reviewer: Gabriel Teodor Pripoae (Bucureşti) MSC: 53B30 53B20 53B50 53C25 PDFBibTeX XMLCite \textit{R. Deszcz} et al., Colloq. Math. 89, No. 1, 81--97 (2001; Zbl 0991.53009) Full Text: DOI
Defever, Filip Contributions to conformally flat semisymmetric and biharmonic submanifolds. (Bijdragen tot de theorie van conform platte, semisymmetrische, en biharmonische deelvariëteiten.) (Dutch. English summary) Zbl 0953.53005 Leuven: Katholieke Univ. Leuven, Afdeling voor Zuivere en Toegepaste Differentiaalmeetkunde, 145 p. (1999). MSC: 53A07 53B25 PDFBibTeX XMLCite \textit{F. Defever}, Bijdragen tot de theorie van conform platte, semisymmetrische, en biharmonische deelvariëteiten (Dutch). Leuven: Katholieke Univ. Leuven, Afdeling voor Zuivere en Toegepaste Differentiaalmeetkunde (1999; Zbl 0953.53005)
Defever, F.; Deszcz, R.; Sentürk, Z.; Verstraelen, L.; Yaprak, S. P. J. Ryan’s problem in semi-Riemannian space forms. (English) Zbl 0952.53013 Glasg. Math. J. 41, No. 2, 271-281 (1999). Reviewer: Ülo Lumiste (Tartu) MSC: 53B25 53B30 PDFBibTeX XMLCite \textit{F. Defever} et al., Glasg. Math. J. 41, No. 2, 271--281 (1999; Zbl 0952.53013) Full Text: DOI
Deszcz, Ryszard; Głogowska, Malgorzata; Hotloś, Marian; Sentürk, Zerrin On certain quasi-Einstein semisymmetric hypersurfaces. (English) Zbl 0955.53029 Ann. Univ. Sci. Budap. Rolando Eőtvős, Sect. Math. 41, 151-164 (1998). Reviewer: Cornelia-Livia Bejan (Iasi) MSC: 53C40 53C25 PDFBibTeX XMLCite \textit{R. Deszcz} et al., Ann. Univ. Sci. Budap. Rolando Eötvös, Sect. Math. 41, 151--164 (1998; Zbl 0955.53029)
Defever, F.; Deszcz, R.; Senturk, Z.; Verstraelen, L.; Yaprak, S. On a problem of P. J. Ryan. (English) Zbl 0896.53024 Kyungpook Math. J. 37, No. 2, 371-376 (1997). Reviewer: A.Bucki (Oklahoma City) MSC: 53B30 53B20 PDFBibTeX XMLCite \textit{F. Defever} et al., Kyungpook Math. J. 37, No. 2, 371--376 (1997; Zbl 0896.53024)
De, U. C.; Ghosh, J. C. On a type of a semi-symmetric metric connection on a Riemannian manifold. (English) Zbl 0878.53020 Istanb. Üniv. Fen Fak. Mat. Derg. 53(1994), 29-35 (1996). Reviewer: A.Bucki (Oklahoma City) MSC: 53C05 53C20 PDFBibTeX XMLCite \textit{U. C. De} and \textit{J. C. Ghosh}, İstanb. Üniv. Fen Fak. Mat. Derg. 53, 29--35 (1996; Zbl 0878.53020)