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: '92d68179bf571ff3',cH: '9nmlxSZrk31chm8_ouBMDBR_R8BW6JiyGA9.nHUarY0-1744165021-1.2.1.1-zFlwnS4KRz3DdHJt_mJrklchkNHqdIYvBcfVuc2cKX3ywpQh_W0GvZBoRDVo60dB',cUPMDTk: "\/0297.15003?__cf_chl_tk=TQlXQACMRSgxjYy7kcOb_P8GGH8n6iIHPEncSxZGtCw-1744165021-1.0.1.1-gIAWWzeT148bMjhUrIvQDY5Y3.54Cvowq1csyXxeT6Q",cFPWv: 'g',cITimeS: '1744165021',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported_browser_beacon",fa: "\/0297.15003?__cf_chl_f_tk=TQlXQACMRSgxjYy7kcOb_P8GGH8n6iIHPEncSxZGtCw-1744165021-1.0.1.1-gIAWWzeT148bMjhUrIvQDY5Y3.54Cvowq1csyXxeT6Q",md: "N7dkAyR7d3Q1a6kx7f9OJYwJqCw4lg6YqFfhi6q04zg-1744165021-1.2.1.1-CnP2vkNHsOgsl3AmevIjBK7yMPele9uhLpXLh5rLjODsuMAr46TGd8pvmPtci_IGwo89x3lPIGAG9hHa9TlfPNg2oAAyLFx.CMcV_Xc2vLFyXilSHIYn270DLqw4bKO6VOX2Ck_fJXShntIncuO7iOLOcqALuj7eT3RHROObaQ6L6LQJsmv3jSVyu.t1XswVBM8hlP5qGdEqVapUMGmZ60.Apbdu1sFY0qPmMHOvcHMfT.0_UMpaAw4.uS97SyEG0DrrklOkN9WDPIOJmIOGH8imQE2MMxJFtE9OOV8gR3QntU5ZpRXZO16lMl_zJXvDDiwXa6kXcMLP03K83C_YwuJa0_Ssho6ujjotO0POam1eKyQs9R06fD8mMqnuwin_HV3vNlnXaGZOvRinVt9niTGQgsfvZ9_PM4Ax9KGwEcDKA5bY7MD0uAUcC.N5wBP1nzW9OchNy1NOKae1GhsGopH2kRmJ8GyPLZqs6Vjwjk7JkjamaNmpPb8ZZwGuzr.b6a3plZddico770QrPJSyExUnckvQIAbnzmjrxNv7KcSeQFPRVUlq0SO2qPBFQ7rLZINVB.xptppGK47oHG5ChUMzY1mwvc7TljSbRB0KL4nPcvm7QMMjFRQ26wgHPIg2NapsdUdsxBIQo8eAEVSxMzWRqD9xgDbuNykv02hgx6lmHr6ManTXVR7o0L8e04e9CtzpKhmHhp3BwCMHeeV_g76sQoZocQKxXoKb8gM2JPwHqRvFvdcJTuO7nL5ap7nsz_RDs7JmNYLk8HRUKBugpm4zJmmEFvW36BqVe32nWB1UIm5FceLPj5DWCCOjAZJYUzhbYgMbamDWQVUkzeacBAj3K6zhTl0cK2PB2UAEkvbgQ.EUrLfrtVURtLI7l6RHW1bwKfIHzBBmFev8xGPMq7GjsMI63.7KwwTcxv5UTzOY3vqEQK__Y8jm7BJkn3RsggZ.9wGFRlcYzmIKZ6Ewt_usmRtcsXPQ5QsY.RgWi4glsLnNwkkieyj.0Vd2y9NHU0jhqROPDZumdXGUh.j4M8wWtvGo4yyfoXzIWS6KFlwo9mN9iz.2Yavg5IQI22cC4uNwEcqbNJuw.AXUa3K8M9MvROXHqMiyUr9t9nDr.5URmqGmFpmFGTZosWroEWS5apfz12s7DEyU3iIR_0__8w2.HiKLLMncXp8z9N90dAQ5gJMWioNlWEoXS2Shpb1j",mdrd: "eC6EvFHGcnSgxQs3NSR5KeaRA2qzMfeWa4ERMb8KsT0-1744165021-1.2.1.1-SH1VWWPbIKmlIir5UQZg8gpplCFoGa90E1OCUdeffuB7IInCeVnVVUX7rd6wJ5Z5NY92gRrtF_n1rezqNINbKA2oqgKYEjZlCw94.oUYL8_Qg8V3SdM06qfYMtLMaprBdQe_eGXku0VEpmiUq1Any2MhMM0wcennlEzj28aQRofomVWgNd1jJ9sPj8YVO5YyrLtJesR_3x_f7F3lEEaQw6iPefKYTq47vtU0ulXhHw1bxRK.C50TNDCieudKz1XHH25LcLD10ePdUsNfzq4wmoyOVq2V3cvRemfngxqHj_GaqxLnDdaq0A5Aqu7Rf5A_4CxoEqGIAVxkIWeTrTzb5PTekm3ckreWy8APznwT1B8XkwE1Fnt1l21XMIa1uNaX4A13N3Yw.LEAX35Vn6l5ZVVDYF4skDEc_zLngnjxhxkz0mp3KLZvsrb7LXziAHi62iVjQCEUFLHuWTJkFa51K7btQUz88gT76HMJpeUV7mn7YiHEIeLj9ijgcT34VvmF.vUgzzj28IBGis9_3I8VbJzb5cHMzT7PRkRklaAPV._DZ4wVa4g2cGOgEllYmxMsoS86s2ElpzBq2mh3EixtfSuhJmLdodUWzRF6w9Migepuw7YQIJZ.o.m9uxDy4hzAoszP9O8DOjCvETBLWq0tLknIgnYB5xn.2r6jowb_AcJLWYgb_8axHaikrHwuvdKAQwP2DA_Xfws5snMrVIYFYgbu7YCdbgCie2ZphSN_HIgjVnKz2hlE24buhmGmYnT3QyQm_4NnyQUOotsT3NNVgWM_rtzZD2afrBVEC0cpgUcI8USb9A2ChdWih0NGhkjxsQXbhOO_sCUitUFj2NYahqGr_dmwEY8DYeXYY7rxRrHDfe1Rv0mJB7XGiS2CpUJ8NDJ2h4yIn_H2jj0hOYa4Q48Yc3hulhRMeonj4.PLmMzmIUZfGmKMl22oMUUpYLebqwzFUM0dPzW18A_wgnK7cv6ALgcic26ClzC8TGVz2Z4uJGXdsPtiK2J1Vx99PoFbl0zg30HrBZcqQ23j1DzvkrIeALyUMZbbA0ki9nZUxpzzb87rrU5MxhN3QVey8r9W63T1IagLu7k7pGBf6j8yfAlZggXJYWRi93MGDtNkEAv7mnncKAcgoh_jSd8eknS4D4UVDbr_nz9tbhIrdBgxQkLnEZ2yz9lQKtR98MkLRKove4TmNq_D1jkj8CcooXWoCPjt67MD9y2Sz7raOt4XLsW__DdDI3UlhYVbUkNZ4Z_Cn_Pe4SKbR69.LNyxc0S77ZglrjVi_xjAeMq50KJgF0cS2sPJeob0YUdD65BsswBrSHkQPnn5AluctI.2UgDdi1Ds0te5x1wbKfLzkbnyp6V_p4RLDRFQkH.N796VPdaU8J16MMMJz3jkIgMzLvgkrrW4rd5ayaAybHZtZ_qSRi6ChRm58mJCGfPyKuDPf8nV2itehSXvZpsta2cT7R3mWoDvHEdWUMzD.G2Is_Im7rvEtEKo2BQUQBrAwJC06ONxOJANk6sCf1tuu_uU75iUOoG4h2XBGEdAhv3MYu0YmuaYOJkJJtnZXY7gBTs16EaEHt6kMBUYaVP2nMO_mazhACIv_anmhQE7xQlA2m78ruiXbz9n9ydWQLlou4RD7C407XLRl7u3kpvrBAuzIgaAbSQsXw3O4aEoQFgveK2yfwk0ZG.dyvKU3RzTdMcyGvw93L_vwQRcbUVh0WGfyBUdl5ymIeXGjby9rYCWbsYC9QjhLxQ22.gzKztOfRjG_B7vWSxAWL4NNs3e0AVWRSuQfQBVUT.5YVqolSoBro1jXmylRHfEQL9.OkUVVmZ9bFe6Ok_u1NpBTZiKoSlveK1a.9FIGivCuYmQH1KMLUnw_P5rJ1rNDZFz9VX1QyalGELLPlrUvJ0XuJGkn3Dh_SiqoierySmnrKQ28CkDFJE2RA2N4csoS7dtQpv7DgMTuk40q._srkTpSkbZJywBsGId0km.zs50rU51JLUiwG2UJKeUTzBcxzqtcvsceN3uS1E05iD.3Q__ej6E54SZD5d3"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=92d68179bf571ff3';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, "\/0297.15003?__cf_chl_rt_tk=TQlXQACMRSgxjYy7kcOb_P8GGH8n6iIHPEncSxZGtCw-1744165021-1.0.1.1-gIAWWzeT148bMjhUrIvQDY5Y3.54Cvowq1csyXxeT6Q" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>