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: '92dd9d0a08b3fd0f',cH: 'k0SLsz3591PwjEs_2JW9mSmui4v2blnmZlGxJd_2MDo-1744239551-1.2.1.1-Qf3A7guIvsylVqGmTlRftxkmKep9RSFcjTYt83FTWm8vq394hyImBzpxEjm28C6E',cUPMDTk: "\/0312.65002?__cf_chl_tk=bqR3Q0oaKn_RDhZJSSao_YzNeuEuFSkM0CBRi.fxvq4-1744239551-1.0.1.1-pgmkFmYzbN4bSHFpq4r9lMq1VXlh.MVDLw577Epku4A",cFPWv: 'b',cITimeS: '1744239551',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported_browser_beacon",fa: "\/0312.65002?__cf_chl_f_tk=bqR3Q0oaKn_RDhZJSSao_YzNeuEuFSkM0CBRi.fxvq4-1744239551-1.0.1.1-pgmkFmYzbN4bSHFpq4r9lMq1VXlh.MVDLw577Epku4A",md: "jNpW_7sjEO123zCH.WcaCBXGRx5KY5qUQHLKPT6NBLU-1744239551-1.2.1.1-k33TxefOFgp1BmKTEe1gTZ7Rt6wmNyqSBmapHr98CzQm1kEMqVDeDASUhp1PnaUnS.8KSvpVyRZzfvhOG1Dx7DoDiMxqJ9UDtnNsf89kEL_ZtFU6F5EOlrNCIBwI15kYNvXd_Nwihr2FsthMg3lzNFUql0I8j5iQCc.otn5NKYWmJzJiXZz414HUwhKHPlMne.DnQ861wuNHhMvyEooDRnUwe18MRcXE5IGtSeH4KR1dzm4MrZpbBXoVrAJHUF0FPaENEbOzhtgv4Gs0v99xGkRmjRFtzIoJf6DlUXumxrWZ8gArQX.Tw8McbbN8PLfMSGK8.n8xdMvDa_YVKw2RWoMRJyT3tIWXQQ7YlvHymdn1fUzfUp8ZAmlBQJgi9pGo5yV6PLR_oGJifR9wLzZUpTQ6jE2Nqzj4PnBAxmrLwIjvwi0N44srQnPlkt5ur3Gqwj1uqT65MihfQLwaDO2NLcNYtdaTPbVed7wRfb.vrZwHo.RuPIUrjiG1pIpHdkKkw4vDhxkuo1LK7jhxf1c7z6MvHExC7mqv0QNK54jK2A_xVx.StuqUfkRiIUl_BQrZNZin5FKVJUxKYVkRNVd1BH.9oPH94itb1G71EJFaZP5i..NBS64AiYlxefFYv4nhvwGUqzaQN57wjyt5lrfVVjlZ31R.2AUIVF2Ol1_92tztDpYZme8Xelp959SREM9OSqZwrHbrK40MZ32.9hrfzF3.9XXRrhXBUBDJBuvtIbdI4Q5nTFtBgUyWig818NiaZ6Oqpa_YRowM0e7JRlsFrbcjKwG4.jzdsmlO6Mh6nmRRYsWKgNmiEFSfL0sp7mdzbf5WsbmJF19o1pDAO7xidNM7wtWnTnPQejoXAGKxCcM23YyoHnrSYvTz_i9djg8xC6bedcZJTqfl4mV4afzobuDvnPlyudbMsgk4eNniVrrHqmCbGQnu59Yb1NswlbooO6YJG6TfcIKiXQ6RPkv7OhioyuxIa3bGFsQcySbcLLzJYLvu7FzmKFHJ96mnuKKmrRja1flKSyJgXIocyyIEwgyzjeB8U9jJcuEa4DwAtxRw48IOoMIp88rd9lTQpZyq9VRvaGxpxTo9EBkNLcBsQe6MNlr14rIQUZZn5c497.ea_37dBBYLW3wjnU5k3z.MOqM4LkQLt4Skz6pWRn0DRCYq3PDHOwqbFx2dAwGbcydOnNDzcR1ZmYDxUIwcqJKx",mdrd: "GD.zW3fxolIVedYm0t3hMvLdnwLqZ7HMVxUFCihZeUs-1744239551-1.2.1.1-1Cs4iCMGK1q_9WzfTBuPRoNnj14U5voPs3uosdEvChC8AwACC16Kgt9Vd6.0AGwMP8Gm2voxlpe8b.Sz37HNcCWmfyd3Tuc.0LVET4jvn1_1dEZZkHvHgIRm81JVM4HjJa55aFMs7HU0TIio5vMEbADj1SYQ82Yhm4xbKrfBqPTzmKtZXqfIRBeD1yWdQ3phYcFt2OVh3IRUB_LnogqtKRsLR3iF_ORA19aXGZOlv3CZMwxDTFju_qSHL8.z5vg7XmbKQlBMdUPjd5nmgz0.Uo53aTFRI9wHMIL.4oWexAhErKNbpidnma0wzfbXioTUxRY2M6nfVduz68GyQ8cRlwMz14wtM9gwn64NLFP8r6uDuaj1iQ5w8_R8ZBmTI8KyEbzSvY6San5m4ohHQO7mRZ0g2YDY_lxAi01440IYm1BT0JZ_CbZt9JPu1yIJhFSgSdxd1EApFoI8xD1mLkeekWVMcLg2yH_F.2ahQAQNZA6tYWLKD73SBfCXodjwcVXZCLcUk5UL7nVePr1PbgWpnl_MRW9E1cuB1u7EiJZJX9__u56B2faprasL4I45Ka8DAz3_F0yKcUIYiv0xv.a7RjJVi6TtbULjOp0rVXCBdNgmzA6KEyaVEyRVjv.ROU5X_Zk33v2GCh4XzqRjdZ8_ajFUbV15L6Q2C.XIk70IWb4VEtxoFO49R8C5hAaLs7lFWwCuU7tiIwWsrMGP825sjhUKinlkH8Fx.IRzq8_.Yfis2kmMjAvcDrhqIOeDa5hDNFD9LgeN_83AVyAHn95nyF15OKle9OEyQDN0SYngbe82jfCpcn7J2uCgmQlS5UsCJZA4mpw.My5rLzg6LTObDG_ToSvPX_4Q1t.YEW4cgmpw8eZNwL4e6c4PfyCxUJCbYGpZL1QXFIcAhzFbHpribY5EJgNp2xQbOTmZVZFAU5Sa2_PuD9GOM1kjzWJ6wbYL3xabZuQGZm6cwpPVPL_X.0SKHwLjJeAAYCsEHp0xH4ARqBN0dPciR1coQ0.Tgee6A3Uxqh4vyZomoZYpCgrL9i_KBtmsFkrJAJGNpKWJf0xpyib5dN.YzCB73JwDxA6XbMabbuHbl9_f2WfyPk04WzArABOpq6AtqP6hdAHFhB7IyfIwYiCOTMzBIasqCTQZ6o51p_godjDIN1jx4Ff07sRCvzozXQO5AhxEVBZABNh_HP2gIMDnlmE_dflxXR.7qMOebZ4PDvlzZ9cqITzlXXWUEyMVlqmZolpePKr_xMH_N47r69mdRtq3Fki9BLipuQes115oMSDg8h6IvNdbWZXVgaDd2hOHxeCGn.ZWfQtCv6ZXe5XxgCAwnpSR4_dwNjruB6NAbdzUIyul2bs9gb0F_LCK2HoeUGzexXSE1AR4GOXE4exFOEFznsiuWXz6TYTNdO8kKfBUyHy3i2tt_9iEpuLx5qPZT152kSEVjasF82yaFY5xt.IvNh0z6NYmLYWYpNZNJGh7aYWoz7gWYMwsza7nXq.MUSswzyYe6sewh17YFCwJB3TGEmb8cLUA2MB9RvfKvAy10kUMcUZvE17XdvuHF1bL.OxOI4W_ifV7praH.DGtAnkOJ7aZC3gyV9WVL8K4fYsYADYts5rz.mFypFwyy9zhig9CIP.tBZznk83RXZwtatepjshIpa9YNOe_SUdJ17aAxyr7d7UqQUCLmaOqu1A6XnKuKoPtLDydnHXEikSECT6znXi1MT.UMR0USyP8DA59l8OmAsOnsKtestB0pqS3Wx5ePQoM6tj8IshE4rn7.Ve74dDTp7EbCRK2VBpl9Ww.p82r.qsz4B7cD6__7OZQe.e1HPI2JbpgPOh9zdGYNZ6kmQn_truIr5Oo4NJ4PkN.mR0TS8Tl5uQ4cA8nMAO.5YxERvPaaWet5sMlCmNEJselgqnyYsPVrkmduZ7hssMa3eo20YwNIUOZfgEsl7THx1asWKycXqP3SZN9EO_Pt.rZftP0RllyolKfjfqtIhUHb3sR4L9B_H7JnX5YLPZtZARn2rx.c_.Aql4Kbuv_nf.Wl1ZjwuA98DO1A5qN4_S5wHjJ_d5rFQ"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=92dd9d0a08b3fd0f';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, "\/0312.65002?__cf_chl_rt_tk=bqR3Q0oaKn_RDhZJSSao_YzNeuEuFSkM0CBRi.fxvq4-1744239551-1.0.1.1-pgmkFmYzbN4bSHFpq4r9lMq1VXlh.MVDLw577Epku4A" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>