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: '92ee0ed4bd5bf8f6',cH: 'Vm2m8jZ1fyKUvUyTS3_4GMByU_pxGxbFXFnrj6U4qkg-1744411984-1.2.1.1-.Rml23r7bKFe3C04LJbwnnxaI2xCbneU52UBSr6kuW.6OMgWn9iOw0rlFJDqk2Rm',cUPMDTk: "\/1405.86013?__cf_chl_tk=aI3oJCgKWGYvOzdhCCyCCQrzs8dAsKaMCC5K6wNh.wg-1744411984-1.0.1.1-SD5fzkabBzFbxxDmzAyunW91jtAPjA1yj4PRMaH2_Tc",cFPWv: 'b',cITimeS: '1744411984',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported_browser_beacon",fa: "\/1405.86013?__cf_chl_f_tk=aI3oJCgKWGYvOzdhCCyCCQrzs8dAsKaMCC5K6wNh.wg-1744411984-1.0.1.1-SD5fzkabBzFbxxDmzAyunW91jtAPjA1yj4PRMaH2_Tc",md: "FlpRdGYreDrHu6mzL7jKQd3Pi7I0pJSf3KYgjMphPeg-1744411984-1.2.1.1-h4NxXGtpBgbX4XeMc7n78SYvYETPXZVSEgdb6wo4.kh26I6UNg66_i5QzMwBpFsP_nPnwRiPuTzPJGXp4AaRFrUsNNlVaf6_tTkubNswF_OgfJU.nn6UzNLZMeLGs5ArbqNwVdIon462LLcsxGweLjCGPSE555VZhu4AbdWkLHHMB0m8x_cZakHYymmoLa8IkGAeiOsu0g8PDfr7d5P7vJ1t.cx.T.WWvwBqX.i5DFDrt5LIcaWDG1t2N1MI_cljp8RSxiRq9CqPFhlliU6fY4nSvbV8sBpvT36xo4HdCYR0YKtlJ2Grz5TdYV7K.o5SaJfu_MATOh6ME1pzhTVgw68cR3kKVEm4uvzNSfeF.09UMLRIlh_n3SiQuPviid.R6PmEk6WABfAKpHGRn1NwIX8C3b6q7O.QiBgbGnn6f60B7JJNJLwoe2c6JW663jAsL.hoIJIXh3qQ9tmul17v4BV19AIIvGqeiGF5zjNeYGlfOXzwmM4GLtTG_dFAVG3wciN6cBYu3Bn2tbeN9sVbpeGZYunUpG58ITMpioSc6WgeObrVmqVQnLTVXvYg489QM9WPsS4lQ880rK3EQFrEqcPeJYC_4lF2XIacKpygV4J8VTv9pq5MiHyr3iXKmGJp34XBCp2ZJiJKlaP.gYwmVQIa8NbIa2LDI0xIhezxfPKQarQzjIirbdrU4DuflrLhr9Tp6PnjtbQBc13NQwMlVvMFnVSbzT9Hn2aGD4Hm2.xzdvgVHu2b1UM6pGV7.vewXTBxCmqzLZYxgTAEO5GkH_xghpHKFxrSiKeZI5DT.p4vqloOEo2Ft017rpiBNorNj3NPVXrg98iBrzjfk9j1h8SLVZmss785L3eEWl0zU_mwH2lI4j.GXkAbFzOEDKI7ZnzGGBy0Vyh.jABx5Lh0hkmGCMqgHOM3QP8zJFcUbIMi_r4taphLzsNC_q6ojHp.OogCKalgm9tTfYveM.DohRM55F5FZameG_wd55IuLm5KlBi2hDXxTYUfC7oWOhluYnEB7uua_xA1Ka_6Yn2KoCWAKb0LyZlA1uKo2rXqu32sIfnj4wJYlJDnllcH66SfUnVVgU40kQaRvR3sYuRNBWUjigCBS0Eb7kDsU6QPZRRQmJKzJ1Dbfbv.IMznoSt6CXNYIr2sQ5REiolvG3hJVno.sz.XigrMggQ.97ysnXeozlnp7UaooTY0_y2qerRf",mdrd: "ovsJwOlR50Qvxh5v2D7lH9P69FNpS.SrWCDvxxS069g-1744411984-1.2.1.1-edzPqV01PpEmU47i8dNrRkYrfd0DEVmjzNDFaRYba5ddW.05hmNJQfNqSlYuQL84qW.6_iQ7SJU8PoWzOoZx8tEIsoAKG7gzGTeGBorT5wpSiSkWIxQDxfe3.w4WERXevyBpIoV8YL7A4Yz51JiMBWdwDk5TRCmOqOIhLcW40SQewlJAgQY7XCvvIDegZn9QqbnKeiAfMwxPliLUt7TR49sczu.FQMxG2j75vjoDNCt1JQx2.W_KDSYF32WL1FObEJ4XPrxPBHbTwd__w4XP2BEw2zRTK9BpFX9WDN2o23lClaM8z2885cgZwFKyKLgcFzYPmZdYnEj.UPKrB13UyCzzAXYrB3pttqjZP2J8_n5UUBiH_O03j9SOiYwG0YMCe4n59gC9OckOO1RV4dfud.r6PPqCM3yDa8YB7Uwmxm4_lSz8kIwlRAzdfdmlIhyHB9_GR0foTUDmaihc7WCfTfA3jYPbnZZoGezwm43F682grMVOxMXbh.mEEh_LFJSJc7UwfutxXYl4jurkXU9bZCCro5rcTyZ5IvCYMa5sNkf4iOE3.wFXVkVXiSoVRmg_PRMAe4W0_B8ag3SIw96GzE_2ga4KpDex.yovuD4HC7rCxJBDa739H32iIyYFWdqV8LrfUE2e7yH26QPiEMyKp3hdYNyiHHujE_ET37.6eTyOf1kq0ThI0Iexx_cxeXo0g2v5JcqOjNY5rX1yz08qaDnABFlLSh0mwdkyfz8iITI294ojxNazRTMSpfMZcGm_rnSecJ664opPg3jag3IKfcdrESKP0fE7lF0PDpp31hh1rvtDc9A1v_TA5SUuz8TaqbgpBIAjaJvelG7q18_YgifrxVdS6Cif09tgzwydGk_QSyz_12iAHyPtfsLN8.V.vVXl_DHeoRVMNwH8XYU1_g8wN5.1hWnWFnMkULPNRHsggQe0Sh2CTkAl7eEQ2vY.KlPMQ19aN6aP0qSYRiFR5x1C3qpOMQoansPX34Qye1D3C.vQ6D7s0AKp5nmDwbZ6eiCcIWWkEpvPaQp_OrtxTyIj0IPFnCY9Oz7zdBhAT2QmDaYqVVYvRTUb1XjstKpbSsyg830B3mgoZOww2z_bTPvd97VtZ4IHTGoqu07fF0IkMbrgP_g9NL5dFwiAXMl.sJcQH4teYJPES8SSXncWRITQCGcoSxCbjLOK115QfWglksYs4dHmihRB6T8riFUDv7f5KUMxy.3mJHKcZiAFc2YDNASDgqu8r91wwbo..ps.HjlhArBONfhUq879XpLW0yhHciRlRcZSOG7iZFWdL84M5.l2AZTF.IQa3CfHHJFNvxs1R8y1O3QIToj31WV46faSAzXTXLiOBnzYke5oBWl8p9LKui8acgR.vo80HPrDy3wRsFtk43uUAqgPxc3lsv0X2J9k1FCVLOyeBMApTJA9Ifp1XkySXcmCvt9Rfzjr1q3.VVp6nqo1tZe9XASSj7OwC3Pp2YTIzTtrJyGoEBDJ.XwcLXE8qFDxVxdjO.rZOxcbP_rpJCTTT1fzVALJ_8q3lJEr_hGEvYyz8iYUmsUQ7_C3nNOgQnIdHKX9ydYXl_N2tMAw4NCVczZcrZNIjGHlHn3pRuND7_sMYJ5PvyW5a4OUeTEwHG7dME472RflNtP_tNybiKBoCOu8O19y4REI7LLQZoC4X5bJ.cHeEzLdT81GtoIKxIMyoWjUHza6eTvNGSEXRAeD_wmYFV86428EuWuojfUrhoBtezbBsENLDmPmG0RAuzHVQ1MJD0kUVxZSIeDJrsZzCOHM8UJfOqeiLjJFe_PXL6ebZuXvGk.uPTnfxItNU_0sCiulmfxirVZrDKg3tQI7A0V7j4W7A2I_l4JDZgkNJCm98PCa7F6HkkvK7.CNrzGWcqKi9bEQXJD1tgPdKgRjNgL.IRMmXAYNms66OxJ8rrLJdhLHqLhTI1AOJTOStYTTQ77bzuYPSIsw3BC8knYcoKqKPW2DwZgzC.ED7BANiG_ESs9dXtN3blVzNRUwBqAqAhpkFkNMriwUZpMl7nEZep7EmnFiKWOWprCG43wiIDdWJzlw_g"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=92ee0ed4bd5bf8f6';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, "\/1405.86013?__cf_chl_rt_tk=aI3oJCgKWGYvOzdhCCyCCQrzs8dAsKaMCC5K6wNh.wg-1744411984-1.0.1.1-SD5fzkabBzFbxxDmzAyunW91jtAPjA1yj4PRMaH2_Tc" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>