CINXE.COM

<!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: '92d4ba965fa63dad',cH: 'dFcr7QdiwHaWRNAYD06F8F6XyWXgqWIF0I5YUQ7KLo0-1744146389-1.2.1.1-SHCG5V1fXpGiHYHD.aF.jSxzFVRecS493rCc7XXg_6vaicWS6IGQ3x65s95WlAFV',cUPMDTk: "\/0687.35071?__cf_chl_tk=ODo7QR26Ukca.k2QJ_kvelboGnT8WR2raA7TjFAuzbI-1744146389-1.0.1.1-zkIs5IA5rFOlmqX7gSgPATxWiQRs6aNW4wbUMLNaIHY",cFPWv: 'g',cITimeS: '1744146389',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported_browser_beacon",fa: "\/0687.35071?__cf_chl_f_tk=ODo7QR26Ukca.k2QJ_kvelboGnT8WR2raA7TjFAuzbI-1744146389-1.0.1.1-zkIs5IA5rFOlmqX7gSgPATxWiQRs6aNW4wbUMLNaIHY",md: "Dp996vKAtpBnto01U55ONd0yTTOQYSc799OhwmeUulg-1744146389-1.2.1.1-vHygciIGGCLOGOCVtQHDhbSNKGmgepiMj3UZc3rmdzrE5D35BliQ3QEO42ajPo6PZf5ST6z1nfi_Kqa31Czq2uHq1sz1N.LRv4gvq33uOURGMpZYFLZJXBjBW0P5_79GiXeN31r2L0wQhbDw.ZmXYau0usH44djfLeeWmBaiyUe4ESOXsaiBbayMLJ8Cjvz3hOWqJKjyQ2FSrfsejlflz2Gige1ih9HEyvWgFSl2VMVNh98PnLYv0fVvl6saDzQlazTX3OeimqSMh6vbRx2PIjlKTxIMTpoUShKa6C6w97HVrtSz998WHW6TmY8jFGvBPbVqnou3CmAyjMYJ7Jcyl2jM37Yq0P.drgy0.YgEBjRJjXcSR8FzMG4DWdoC.ZvIlI3xWQVrvqplwpzEyfzYVup8jYSxo86373rpG1S8Eu8TXHkVTwgc0O2ecJbBZGUL3E8tgXJ7fGvSkTlg4_B3m4Qz9JvTE9lxf_4qzHOJ_rPh2Jz0hCkbMv6clMK512JfrHEhfp20qhOcR0_cF.rF7csPWLvre2a7yLj5GDO2LhwNfAo_7wp4t9mfa4HIH0pyPaedk37EU7u8QSxbnbcWmNLByrWlDN9jA0bk1yGWU61zXcoOtOB99iOBq7cYKKhWbmq0NBqZlg6snSWc1JtJlt3R_GkpFBIrYokonwdGG1Y.g9dI5BK4atQO3SamPEheQC1y4W6M3yMH3STfPtRe0GEbi7cRIVYaQOfiDGO.XcDen4qb.fa0O5FFSL3VtT1WVZFZoXPa_mNZV4CGEYY6amvPnUabw5CgIZQAqiIwhPwQ9hSq4LNkBQ4RKxETlBPim_9dkGyFmPCLK80kK4gUyK9e88rpAMAMetx3CU2CQ9AA9aKDuoqP08S0JR90p6i1gbZjV5M2nUXJrAvbZRVn9amNNsdkUrf2nU2s0fCljnNujzinHqJe_nV3F_XJmcVB0F4g_zd8_UhivJn6OcFZXlj271jYfiovGTmLPBx.YvTJnpK_xh4FxFZI.QUsidf0lJszUOL3ht5NmqZ3Xv8vzpuvgLWdIGqPEYjQFRVLVFazjCZuJKZqNs0OR3X7BDfPXOIUSp7jvC.ExBPRXsfY0Utinmfb6ob1umA6gnotsqAtvC4PsCxD53fIROe5wwv5dLLkHo0XU3EMIhhuRjzy9KjLKZVwUkl1MD6L_uh1CHbJu3XE_QJnbdWKsnZndaW6",mdrd: "J4WgBDJAo1DHAsWFrG07L6c4vNYKNFcYrE.rgJ5LKhc-1744146389-1.2.1.1-50HReN11GOtTd0Kf2iYxC0cjS5g36aa89UxiZ90kvicMm2RIwDkYbkg2V.w_thR.44VPjUaR7wIw4L0MccQPQmTruijU5vY.k_yIPxSpD1zY4.iP5nOA_Di3QDY5nDInFMdczaKnfTuicw88ZP2oTwa867UKuJKSDlX6VEZFqa8MNvl4FIHd.ENK1SHig0OZgyPSF4s5vksGSmakvQHHEVEpgV46t6CmBpCBugFB6A8sKL98s2bzwa7nt76XiEAnlbo_gxSVarltoC.tSUAKapwXURfYfcxwsRqsc3ZG_XCVaYPQjid_JgFuAgQWfaIkyIHJHQydu8obk8LcHrrxHr6iYRUINeONcCXjZX9p9PTIofy0LZKVVhIP11v2xcIcLh0yzyojKOvqgwJdy3TcIeMMBqW43GZu_Pn0qjzQ2Efeh0ZfUmtQmmv4dR7xr1Xm1Ws5MU7cf5Dj.oOmEFUDR9HpB2piOacPr57HnHMMjGr70SLbuFC.irKvM4NEo2zdFkzy.7dWXRzXJnzARDOKkyXZw.V0PFVAzahBdyxkX3G7YKtj_uVVp_fSHjPKMi6rh9vy5u496GdwBybz1ZkvZ8GuTllqxjwyRyYsfIqxdLCwlRhZ6iraozfCw6tJRcm2ygq.9A87CbjAG1DCHEcLyYjVpnFPHWbDoWhuePSvLr1d8EozeLb7ox1aImBqXzimx164BXNZiQsFDfbskySQ_vhxjVtCQZkUz24mydBnN0Khs.TIqReSyMVYVoRtWrFo7oJB8cR.4DpAwkd4_F9a46B2JSlwn0L.jjzf9M95y5__3MiNIZxrBZNxKaur9XmB9Kd4hztldAQvwjpwNvIB3KVjDXwyXU6jpux9QfJJAfHWq81IvMbXReg31iGPPdg_0ho5GafDqnbMz.1duB.CxEEin.sXksAZAARy9RUxol3riyLj8sSfPcj4K.3E2Y9KJ6kezNEXEOl6OArUtRGCq4LjpNup2Zi48U8UtI.UZVhLbTw9rGImA9W5zFFS9T8ElHkbwpmk.FvvDhcScnI66GVWmynjsRzdhF0zLZlB6mEafh2.sbW2yT4HQiB63mhCDCIflDmG_RTXmQSoBaKQ73o9AKj6MqzzX58jmNGF227QgKzSdBJNSViNl4CYQBeUHAM9bwlwMz7mHZb06gVkkz8qYlprJ8v98n_KUsMYZGYjIAwUhrqTfVQxhd9ZTztcsn5P.LC8WX3j8xpqkBurR0oUAFiL77lIh3GtmPPgsb3h8UanlSUNMpep4pC8bV4xnyjpSha_o46VM01HDzHMX_LMp.fqVac4mEF4fTbrfQbCeDiQbGqqaXVRZ7xRpiDMUEkS8K4QLGnol3y63qtfgAcvLUHAOEnfIHERg8.qSiOUHWcP.Wcb1JWJyaC_rkXl9I6VI34kBxFKGiee4sI1rHdNGe6jCuPWuwXwXofglW1lmRGHKpsKBoES31.VJuLnrD0u4814FGHJ12maUD.XJP3JlpWU2yELVfWn7cxJYqBadhClW0wVGfO0V.1riBTQh4iTwcsQ2wFYjewnCVDMJ4fjNMeeOXyFw57rE7_uydOdWK5FMRzBgkCn8uI7kP_cZRhHl1GGIcHBZiBEFJlcdUQx85EXw73Y7q3vHCXm09Qw4vAzbnUViWe6JwrQ3.wM3eoPA9Rc1L55SH6ssp0uu6aKLpxDuG5AdiOD3updJLwhLjM9IyMxWXmpLZ.2zvmOxV3vruJG4GNEhLE04rOP769n3StuDDQiEbgXtxU4DvBmkMOK.kZPcVM9NbkHdiD8vMqPS5M1Nc3cIIqmJj_CYTkHfN8hGZx_3AIvA5c2MKSxDW6rVHnuIyi1Ug_1q07VGcmd54bJ2H8MXNxBy7I5H8qI6S54sMORqKz3OL2I4.fb0bOQq7y_0hn0CHC7uRWCl7u5tqUA.oUy6wzBiigRuYpL.bOmXm4HsCZi_aaJsTdzupO3mAMWf.RaQqlcoVng_wKfsHyl3h00MTD7L0mITarXkzoR49VZnkFjGHlnYG5wmDDqFXdUPnlLqCkKfY66VwmV6fdYgeNllakX4j1xwQ"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=92d4ba965fa63dad';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, "\/0687.35071?__cf_chl_rt_tk=ODo7QR26Ukca.k2QJ_kvelboGnT8WR2raA7TjFAuzbI-1744146389-1.0.1.1-zkIs5IA5rFOlmqX7gSgPATxWiQRs6aNW4wbUMLNaIHY" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>