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: '92de58613dad2ee6',cH: 'cupNeUA_ctAn5.K15wrEJyw3KFBEZ8Qk9_N9WYJnVKg-1744247224-1.2.1.1-VqNUnbLB6D3sPI1MmUUv02kS6ZBihrDbzOp8gul6bjjENa8h30GKrtbhaD.9DQNA',cUPMDTk: "\/1406.65045?__cf_chl_tk=qA0N3Jbkp3Xhp1k44UmpdpbzCWuFA6RPoghuQrEwfPM-1744247224-1.0.1.1-_qxsQwhZfIxpq.I7CGgUfzxP3hBvtuvUCTT8PLJ7X0U",cFPWv: 'b',cITimeS: '1744247224',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported_browser_beacon",fa: "\/1406.65045?__cf_chl_f_tk=qA0N3Jbkp3Xhp1k44UmpdpbzCWuFA6RPoghuQrEwfPM-1744247224-1.0.1.1-_qxsQwhZfIxpq.I7CGgUfzxP3hBvtuvUCTT8PLJ7X0U",md: "QYbRSdm5kkHDHKjb0jAZLtR7FowEIa1goNvrvGO0wsQ-1744247224-1.2.1.1-z7vUJAsCnU1wCTqOUSxJZHSnHQn53Q2vMU.t2tad3PbFk_xc1KC71bCkkoB0KYtw.RQRzYb.hNF_6.wQz2p2O9fzdBsVHuX26Syl73uK9GGeg5KZ1tzT_CgGVskQNDsMAW.hlBl5k_c2ZRBSv01i_wJl.Ex0kzEs3nucXHB0XaEqgTdD9XSrSvkY9XYvkvYjwL6DK0iOKCgFUa3.waxWSg98rl3qEoRxHTk52_Wlw7VW1BD8WY70gahIJKuTUVH35HaZq.LCLb2MnJ71sUqeOH7_vNmsrytYHpBJRHucxUIBbacry4.KtL5RS9Yja5ducq80pHXzhtORUdsHWSL.E7f6eC.T6MBnvMYy5nyp8o9SxFlVbdPpfsqsiuavKhJoqlAznu06Jb9IdENpgA_GeziLXZieAsgfwoC6JhXAt.VWTVSj1TIP74zgvD5Bfr1NY6ILNb64cZdBCOj_lapKaIo9EPY7zVYrBxebUx7Ip4g9T3Ej2XvXOH3L0t7FN7lxST8t5XRR0G0vFFNDU2CGlr6U9q7zDV6TfID2L5n.PneYfFTfXU5DPtN961X8mV4j7ExRYH_Xp9.v4yGyRuUOPb18cV7Q00Tm5xia20PZJvXzwkV5JGloY4Li0ZfY2shVmegRL1qTZ9eLsYjpFKFnY4JYruSnzvtI1bjK1bXxV0vHgyeXpUrBxO3yBptY1XopdJEg6r_kuSKeUdN2aMUveKGmt53CtPrDtaQSfXqa5RMgleBKvK4s5JnEy9hOeGlyPEWbkQ4bg7nzQt1SkWMZdsFe6RGqEDJEXc7Oa1Afl6O0iKxjDfbrz5w9jjJi7liC2OlsWxREkOpZeWuR2B8PQkK5uj_i9os5aNMcTMQ1iTNAfLZSd7ZXrH2DPgcV2753CImCcQ7qLdxnYx1qHBOHGTOBEZi6jf1jXm0kBumhfYkYkAfNY63VuNzSL4XNIWVzFa6.rz5Hj94yIazQK3mEeB0tcxgZlxNgDQct9FY37aUAPOv5ZaFYwLiXwciNwDS1rLKktxozZvFgs_m_6wzAo0rynJH7PZ304lgkuztBHQFzz3bB66q5UqBeHhrD1ifQci8CHd15j3brmi0_kPAr44dPpDaf4oWqCzW_PwbuhwN9ZahA_hHSuKE5VYdMJ.90XAr4RRKU0viG7leohyBNCfHuQGflcE09NO8zhKmP8FwkF03ejld2GkqrtyGnXB_b",mdrd: "MjSU_k0BFA3ke3MyMqWzSwnCvmswNRB4DDwToVowIB8-1744247224-1.2.1.1-Yx_jRQNmRQh_q22oktjRNO5KZPx2UD1ZIO0ul7LFMoeTviT6GnX1UYJu.lxvooWP7PIVD8PmLrgz.XZ93J.KHav5.9zI9AIqVuI4eICnfA_nm_IXzYg8drzXrZqLvYIRzJ78IR4N_.EOgySzH7X6sfEmhCUuMd22KdhtZzqw6PBQfC1T7UuMmGeVrQ6ggwooc7xSeNwxribWRWcL16E_7byOlEWrj0HVr7HoWglmKySactyOdOacB0p8NKNxcRZ3HaQEjBoDLOZp.d4DNnbJv.aqxOvb1oQGLA_lr.QQHWtW.dppEtn7Ug6dEyqf_HY6WG7Q9ZxCu07olDVhFkhy.69tz38aLuGWQck6rUlT5GuX5KilWvLIpXbyKAgZ16eFXXhj.cCGEY1EEs8c0Lq1bF_14PXPuNHpw9ry0v6AX1dpvcXRaQh9Izp6peFvz41.QOq7IcZO6MveW91q3whuCwLKXu0nAI0et7joqBQN.262X_7ARWaiI3557bKy8mvz9e9W_Eo2Y4HzVmutaKeXVwq4W1aGt1zM3B5xFzXXM0OVjEJQVCEFT.9QQYI7uKnBD7tJg.eYu46bndvDjc8DhE3VfVqPvbZSkQKS58XUBcT1ahOPw6HBPFl.v9qMbwMECTBf1t4UXGHaUkxi6VUHP_zIQaJb6U1LRTKMf8nQAmriTtmji_1eY1dVUogdOVb7ihHL3jSpyWXrNr8a6qFKReCaWIHSn6ATuaZXlqo__g0Tv48nXRRCFo0zXFO0FlkyOuvxasJdmvMc7JfVWRtOG6r2bkYkTYlLa7cN8FgenJnULD2EjKiSzNBq5QiX42FOEfgW83y99LJExPdq.Q8aZFXs9zg1obE8mrWGYN4YABz2tQtRybHKNJxQNXCscCaUgeSp218uaqjm9TzhRWke17_3Noxdmaqv.jdxaJgD904ibpakEmfZ9NN2c3SayvcqTuv1qmph6vVZ39taiD8GBiNtEt8jVEcsbvwLcplPCa4uVP7brqmEwPhj3U0VkoFDFrRMp.9LpPUxvI10eLRIn4Z2GTEssJAzLXlZTKhjU9sGapZSo2gnp_h6jqmLVRzAkJ_ZQQtNZiBVKvdlXxLngVFCMT1myamhdTj8l6CiWV6zJQ.T1MIPpVMbOwPEp1oBqYgpsFVMfVXpDNsqO6qvXZa9Dbc_SJrduQ4K4ZkpKTdula4BpuNkfIvb1gjcLMoFlDhcYfr5kTclwxNw2eixHo6w6kJ6GDh9nl8iFpJ2EI1OVmYTYzi_5u_Mw4Q2KTySB6dfhB1aJRok5s_pDJC5uHhENDUObqo4PWc8bAkkGp11aHTuyURqp3r.5kI6E4V0OBcebaY9jXbFwJSzbvG6HvwgveecxZM9PSi1POG8uj1vJtlwSAeot1mISgkyCHc1BXD0R9gK3yEmkaKZsDqmJabIsF5G2TTQqdJu7_YTwWMKn1M6.HiNKIJ9GTGg3swp1clVfd3BnsedeTk53MATRvzcv1ZktWh3QZjBvX9vnjZzLpW8bBaNyunIDfsyygIIM4Ik80NvWpXEtvzjfZPeKzc8LGZEcJxq.T7.JdycJQbbQ4TYlMQnnrQUD6BoVlfqFQeGzl6.CCIcF9QqkRsG7lEnZrMzs4raMeq5.fydkmEoPfjk3M6AQf92KodelqON_x9E5M0S4.GhZsWduEH5nopdCTRVfVlFy3HfT5fpNO4CuTl7BmqKjy6BzJ3IH9nkbE26db76.RdzyIVdDmV6fQuldQS0ClxfMdebsh.IOEGybAPk4AvOhsBtJlZpsYFYc5OSSrBlgYrRdQy0fQA_CtKBxATxlW9vA4jKlLCqlOMTC2Qs5iF8LYNWTa.7kPDBEbBm2YbUdpjvD__gpntXp.nIwEh0B9NEQLOtFfzcSg8wv_pukITjq4KAuu_S7kk.4EgEds9eSZnUkJtey51jltBmmrJ5Q0Zwc2a4h9eJ3zZRkRWYMBHE4IfM73NE5.ituUcQL9uHp8F3ctgiQbvKEk_62GnpfQAdudYlwuCWyhGiQIlxr.ghE4ElqVIrk2fN"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=92de58613dad2ee6';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, "\/1406.65045?__cf_chl_rt_tk=qA0N3Jbkp3Xhp1k44UmpdpbzCWuFA6RPoghuQrEwfPM-1744247224-1.0.1.1-_qxsQwhZfIxpq.I7CGgUfzxP3hBvtuvUCTT8PLJ7X0U" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>