CINXE.COM
Just a moment...
<!DOCTYPE html><html lang="en-US"><head><title>Just a moment...</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><meta name="robots" content="noindex,nofollow"><meta name="viewport" content="width=device-width,initial-scale=1"><style>*{box-sizing:border-box;margin:0;padding:0}html{line-height:1.15;-webkit-text-size-adjust:100%;color:#313131;font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji}body{display:flex;flex-direction:column;height:100vh;min-height:100vh}.main-content{margin:8rem auto;max-width:60rem;padding-left:1.5rem}@media (width <= 720px){.main-content{margin-top:4rem}}.h2{font-size:1.5rem;font-weight:500;line-height:2.25rem}@media (width <= 720px){.h2{font-size:1.25rem;line-height:1.5rem}}#challenge-error-text{background-image:url(data:image/svg+xml;base64,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);background-repeat:no-repeat;background-size:contain;padding-left:34px}@media (prefers-color-scheme:dark){body{background-color:#222;color:#d9d9d9}}</style><meta http-equiv="refresh" content="390"></head><body class="no-js"><div class="main-wrapper" role="main"><div class="main-content"><noscript><div class="h2"><span id="challenge-error-text">Enable JavaScript and cookies to continue</span></div></noscript></div></div><script>(function(){window._cf_chl_opt={cvId: '3',cZone: "zbmath.org",cType: 'managed',cRay: '92d7474269b14655',cH: '3F4aFqBTR0.vTmajqQrNFsQqQ3bDJO.GRQXYeZZSitc-1744173122-1.2.1.1-TC7m_fenNOMF_7uMNu04EHJkYPuaJt4ZrilaD304PEBrH2OXgh.bufYv8LQptnqn',cUPMDTk: "\/0980.62079?__cf_chl_tk=bevT6Vds7wTZ9yVucfjZR.Pjwzl5Fs7YXUWx4Gb5I8Q-1744173122-1.0.1.1-HvgWPnVbKFS4b6QFBCQdB_qpE0tUhpEkjmLwqObDmwU",cFPWv: 'g',cITimeS: '1744173122',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported_browser_beacon",fa: "\/0980.62079?__cf_chl_f_tk=bevT6Vds7wTZ9yVucfjZR.Pjwzl5Fs7YXUWx4Gb5I8Q-1744173122-1.0.1.1-HvgWPnVbKFS4b6QFBCQdB_qpE0tUhpEkjmLwqObDmwU",md: "Un.0JIIDSy2MKwBm7ORxEAsSEiqE_.RL3OMtYezM6UY-1744173122-1.2.1.1-fwNoCtmeKryzYHmmi8.VBm66sCao.UVtPxbiplo66sx.XqWmUBGGxIcHdwoDf1DDCVvSy.3Gxrvu0JNmfhxytJx1LMgxVmxkO2lgzjVtvFRpv6NpXHATyveTRSTxRkOg73ocOfruM8q7988h_hs2mMDSrDnAkcyqmDYCHQ90DnleXJfP8bqIpPA5u4big6zT41BkRWhRZpwDodVMiWsvt0ZwStnXojsmu4ovr_peq_0_qbNHkY2TvPkxYtmG4C3AwzVr_01hn5S8GPwAS7on.QHqtc90lJMYlVRNbxdhS9swtzmnQ3WXlG3.JEU0hK8VUo_g1rgVeXXFWOrR7kJQw1fxO1veWrfLtCujGY3QEAzq3iZwYSNAapeYcp4D11voHXO5wllH47.lKBbBeljRGelX0vuRQ0.23aeCYugjzJGa5lJ7ZCZ7RHLDrb79eZBvrYd8Q6AlsDWcCV1FlUDl5IQE5jqrz1.R_mwdN5Rzm_Lgvxt7mTfLdmq.Zti4w7nGwdKx9iEEv36cnkLLngtzHw914XCey0AFMclblE6711JOSN_39zenrYfA5Xiwo3Uzzq104_bou4d_aQyCcZ3.Egd3GS4mO0or4dxuFryihemaX1YANRp0m8Fh1dSkgkpJaBZv8VK8cM3WpO7pYA36mQ4g2_wthtEDnkbLPy77SEKGRKhoJRHSgpun4.Y7waoCilihPiyCUPIZFC4o0aiM0uFUCqZvQXuY1bZlSDk3h0YLpfKve1b6W650iB2HJvoXPf7OFCI6eNfjNperG.JRUDUwV65UiZQgjgqO4_8F6jfIksmGjof2hre4U3Akd41G.jEgrh51VPX2YZ.FWHCaJVijU0xF8E4xXdlqY0tGuVsUHghMXweTCkkghPocSOtUqOZnNFV17V0P76hT7G4hIu4D2kdbAKt4X.kpZt8jp4sKzsua6YNxNX0XL5rbD_duKBbJg.5qZL7eQr4.4iffN_1KGPmRsTNBQEccSdTcb3ixS.9V1galhpEeppWsjZDj71p6h7Z9_YYSAsbv_eakD7DlSgaCzbVDH10pFf1kli7K5coV1iVRn5QeK2QKqEc_YLojbBd27BVATXUoCexfphVVHXNTixHow1ylhwZvOSV9GPgw4RT3zhq78u3_0sHFQGP4F6nhPURp9abWlGKg6l_hj87XmhMhtwbIrIgU5RaI17LMVIolyMd7W8VHJt5U",mdrd: "e_vQQZx1L2tkwzTxHk8V_WdC6WFmZqMJW5BmWwUJeUM-1744173122-1.2.1.1-1B2IoGtqflpdEHCtKQeXG.1vxl0Qu9RCTIbRUX7O8TdZEquNedla0c6fbVDHonXUek1XTIbrI6W9GZxt7YjFndNIN0jJvqh9eSxZ0j5EZ4PjpWfVdm6M9V8_oxb5iC1kKVXK04P1W7QKrlwfhXjAnnqHHTOtJepABQbZ9cU0tvddb_XPAmw68pePDfrijupbdDOc4Cww1vAM1GxHVag8RYZ0kiiMXvezoTNKk_4ozHqk7HC4MREljHaX5jhOj9yPE3qFxBzckoZ2M184x6YH03idd2djQhtpqG8XlwD6Fgx1Fuyxozs9FYxI_U7ni.Qv6CaFv_9bPJhZniVpPGrcD5nZ_WArJolhksQRZST3xhRLPCxLeirkBmCCSm_hUQ5jICDada6YlgZPVFaXf.uYwimG1b8LSGRCZqrjifdlnhRnVtmiclKzViFKNJwfsYXCp1cLKjLc1uvmBWjCPJ.kBq6hoe9n6oNnFc8SPtAdWCV6L_8yMKYIDn9mXLxWa_nWzlxDOrezsKXS6hdDoCrH8AQJd1vHZg7Vl37nInfksr7IKid37lKWAXmwE9sEFboaB_5PCWOPSmnCM0JLtRxSrwbgNUx9hpMIxpxdmGtV3Aj5YP3RmpZMXh0LgFgcbx_0kIv4XMrEQVnC2c_FAs7OKcrqN.eYQHjhWzTFILhmU.zFKt9DO4r05Xf.WuE_o7zX21VTntkGv.PLgoHP9YmhuBBvXch._vA7hN0o6otSeVGgt206UjJk7sCyQ8VpLIAbJWchaqTBTZIJ7CvEkaBr8bxCZWyTUSJU0rXC88cXBXcqVX9ickBJuHt7JT_jS9RxaYHzKpw0SDPg0ERw1iNABNgvojg1d4Xw1PLdCJlMAAUhE1eWuqN5pkyBnIi0kslZTxGCVyObLzea1Zu5V9lDIz_d0wEpdPEIqcEJbq.HyBxcwoXRa7WwpYdcFCnGZmToTkED7FRzYsSf4tSf0OP2Qijq0mb22GqgJuBMiVhBWqkZzOfUEVP7GBZjYyZzfB0L6KEghOu0.mefT7IGsX2SaKKIjUCH5ye3I7s4MGwLqYLRst7Q5O.MkQPUzhdwFqEIJGfrTdxFBfgpYtzv51KCfqRgiPoSn0U8gAPG9TxBBlY7YUQJkKGJWEa_dbR5wC1qJaY0HqEQGjtb5xtcne.rP7FHaTSMWnrY4HP3ykzsfy5ch.N5Tsb5zUgKBQ_ygmqzQ5XBu8DHW1KsT7bqq5RJYLVex0zks6HfDi4Hb2wEG1iKHzEYLyiT1C4dDZz9YlBdRMuUxq0iav0zFrrpgMqUIp2hAOBHYyiUTQMwHlcNlvCz2A_93pqdoKRch2L.BE2PejbH8YkVrxBm1zdWwT17iF8VnCgPI61zzYsDKTOsnrRDzKG6PR_gRZtwTXMALOdbLq3HYxDo6kgD3HiLS8bF9UFgh3SH08TrNE4apgfKHPh2RrIZYKHcIqr2vCZuf8vErxgYbsYPQBHv3gPzbGHhU.L8igm8ysThxqXfJ85qxBPdcTKehJNVqj4k2zw4V9bSAdA32mWQsBTAGQKit8SdKEfEp75xsHqT8OTrJcS.ia0JGHixEz289VTUI7FEk60VpiE55o02AAXqCu2hUjU66rkxqPsNTdO4NGJBWLzRZji4rKhzZz1.ld.VT_dmdCzzGSgS42BE04GARCQ_zIpR1xxk.WFcd1ESzDaV_YtF9HF96IFdcKCWOu9hPQTh2dRr27z2dBt55zidmKVdHyfgKORhZUw.Xj_mrboTzyC.bbzdTKv5FV64TjX6k56XZ.bkQLwtwvqxWasLZ0alghBvoZYZxS1g7Q7K2bnarQXgGc3SWGylZWHxKsyIBTHmLni6x1Wll_2.Px9goyky8w5ZkHWmntdwtgIkuduZjWPgQIpvaMurZhdjOwaL4whIzDXmWzzMpT6V_qtpj_qbUlzEzMbDL_e0UrHPO7In71OjzSQi5v_E_ys3NnB_e4okl2eZ7v6lJ5j6K3O9tdANQsNoBKFxUczrHapJInU52Rpw2q5rQtaN2rPdMIKQ7aNvuEPW"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=92d7474269b14655';window._cf_chl_opt.cOgUHash = location.hash === '' && location.href.indexOf('#') !== -1 ? '#' : location.hash;window._cf_chl_opt.cOgUQuery = location.search === '' && location.href.slice(0, location.href.length - window._cf_chl_opt.cOgUHash.length).indexOf('?') !== -1 ? '?' : location.search;if (window.history && window.history.replaceState) {var ogU = location.pathname + window._cf_chl_opt.cOgUQuery + window._cf_chl_opt.cOgUHash;history.replaceState(null, null, "\/0980.62079?__cf_chl_rt_tk=bevT6Vds7wTZ9yVucfjZR.Pjwzl5Fs7YXUWx4Gb5I8Q-1744173122-1.0.1.1-HvgWPnVbKFS4b6QFBCQdB_qpE0tUhpEkjmLwqObDmwU" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>