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: '92e160d7eadfce16',cH: 'Ar0jyJ3G6bThVRLi4S7WJsCqqY44HPzVGw7M5tYY.Vc-1744279028-1.2.1.1-XjRYNcyWOEpx6Cuk0wLE7uxEazCb8a7sVaTiF06GyxV.LQqVQnlyk0Y2kx7EHwtM',cUPMDTk: "\/0090.33503?__cf_chl_tk=0KvijhBI1_PtXBuQgI9UgcK5xV6sv1WGEwSAWoiLfxU-1744279028-1.0.1.1-6mJ6QYDgHPQTSxKQjbBDRaogI5bg7go.d_W.kea1F4M",cFPWv: 'b',cITimeS: '1744279028',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported_browser_beacon",fa: "\/0090.33503?__cf_chl_f_tk=0KvijhBI1_PtXBuQgI9UgcK5xV6sv1WGEwSAWoiLfxU-1744279028-1.0.1.1-6mJ6QYDgHPQTSxKQjbBDRaogI5bg7go.d_W.kea1F4M",md: "rfnLdNMGiJLeFxRYgHoeUH5N0kDfOeibNPC2Rq_uc1s-1744279028-1.2.1.1-uQOQasjtGus86kBtb92x7xCxls3bYXj5Qoa_XEZ6SnS3RHpuMMZ10xPtwWfecl4Xq_ZlUMs3on3g95XJq28EnoikVuhtVerprUPv_vu3TzB5Ml4_H1KwnIxrFmHA_zoNNm0XTfidu21YwaTefs9XkHq997jVz739uJskTUf8SFZXCf2_y45Yc3eOPYcyunTCe0C1FLo5v2w7HjAZWvtmKiMnmK5FpYfJFAUsZZg.u0D65xOOBHUR11cf3nQtX_UEE.LEMyRIlf1EmIqLKGtqeulyECBMwUbJHWal.1Ylqms.ZIFjR57AECSoK64VXJgPjUJpC8XVtoYAW7_2oKqiAT36QjMYOhn6C3pNwJBzPSeKQ0RT.8StuDqTnXADJUDeuRuFrDihuWj40tF3lSXniM1u_5e2KDFsycD2OXFQ7g3Fsqn7VNnq7wVyPZZGHlNicmPsbYSNIxQQDb28sHJx8Wg6sXKD1JGxHBzZ8jo5ZULXqxcea339A3Et.puz7KzaJYyC0vbER_C8MTUQH.Lg9EA7oXQJLcBu1WWPIr_NAEp7eY3tmkqQ3qf1LsakV.n9fm..5L9nxqCjtmLlfbxiLCQ4zc0diP6fw811fm3AxMaI_9mbPVpU.InfXHZCjo9oOXJbn6xeiLpZF0fosY9h92oxjNp7vb.XlYvfdYN1AuwPpnE0obhugZgaAw1q7MCKlyLHE6E_tHpGV7OOOffedSREYdRbc0725gNO7aRaSrDryi_N0w6aEBRglBTlaWqNvpLh_Qxtj6AQDZu4KQ.ZSmu91fChrYBNKmk4cr31cqNFDDI_XrQT7RexVR3H26kZycx7.N_0jkKIG8XYueX5kHq9ai4pJg2r12GX.REtofsS4CXnSxD0hzFov9rkZjiBZO_b9ZXujewQWJWqeg._G.Edf.CLUVl4gbjIDK5TFcloW3vb2auYJy9OzqgoqoPD4Bt_EyNDaizNf7zS9rxhbkkTg1.eaYAalQA32EmfEHPGRh_Zc5XBeX_lFs.kc9TBCy.PRrr_3JMRrKfpAr1a0mAtZcidnn9NhxFlJBCGqWRpG8d4zleYz6VgAoXUpkrTB9Cu5cZpF.galI.2wPujOOCk1E3Xcuf0cUvTY_3YjjYWMK6VOmHoLtQEVBLXdggIBNAbLsu9yDoyN7JzGdS5Jg_y4YiEWE_tVExz5iD_S7Du_gbgR85lLtEs5B52.bVE",mdrd: "loK7E7WDkjExMrSIBGyeMHAZfGk1PFacaYqZUsKgGbw-1744279028-1.2.1.1-DZF4nE193a8AVNgJZ15Hqmmlh1IIOVQV0XLsJjFjk.bjAtlN60I9L37kPw_inWB7q5osNqJLOhVl_Pdnun7.dTFVtStgqjywQiD8m1xyHLQE2o3pW56EVQxnaCqu14znC0QECeevbEtH8HEI94HAtfD5BHMFoG2RwZCvpjTti8jAzUdJl5_4QoTSbTfH2rvmUNqTEr8a4d1vLznw_Fy_u.znhl8jAoR20mA8RQtlYaZOViJwjO5QsWho.dy66pNjXzQG.3RKVCLA_HCK9V6dFaPwSsf2d7sPmRHxIlq8b94c_vgsN3KkM1GnOBa8mdV_UUs2hqbRBRx48H1M9Qu_pRCpt10C7z5bpvyt0UFOsoTRSitu3674URpnWPHqnfe19QftKMUGnpTpAEZaoErn28sWYmjF0lhweMjKS7tJnVsSRUtNbZCzhfToDRAHgInSVNax0LnbxXXDepkQbzzQuzgPNc2Gig.F274tXAS.FDbQvdq_cfFMnk4fwBkFLj4Pi7SIkdDJih23JdbEtl4k3F.WJeAeYSyNru.ZomcgEu.2QMxE71le9Iqi0XlPr9LA7po4qrKWFisp0cX0t9EiZNA4UI4WThnMYQeKQli4EQeKhlSzXPmWzFBamtWDd.TB_kqYDXodIvMg396MKABaQsUhWXKioeO9xFlm1p1LYwn_Vsrhqn2fY3M5PbkSETZ4UvrJXNFTztzgdelm2ncLir.kBLyUakH8H3wAfDg1lLs4PjJAfHSj1rCS6JOcb0V3MnZrwM3VvpUk_LW79gyIQgop5AMbNxeBvilakBfPh9Q01dlho0hl7.aeoFM2C7ypmR_93XrQcS_bO2BvevRI4mT9G20KX52Xz6QcHTQpHlX_5AjobKFkWAgTLirKvbBhjhF4QRgwy3IiNzx_JmyP64pNnPt_E1COfFRVHu0159t8pUohJNTo2H2zmhdexBYxQ29ZrBtEiRfLSpJIixpQfWUYSg508RGjWVH.6wLVKwqjg3dMmeEVg7Jnu5DBIi29uQEIdu8yGcm0kHEjnpEcinUheZo394wPOihC2UkPaVO7AIaAaMm3mZcgFTatgHkTXeYlQdIDi7_IlocG_rcvwZ5lTuxx_9UGhxYwJP13G8OxriBXVokqy.Ew6c54wNVNCfzBxjv2EAuuBMH3lkTRHjWWQM5a33Z8rY3RXx7t17dJNgzS3zOfUM7lcmQ06H2NSh_4C2uGNviflq51dqKfFLW7ZFBcEo4sBsiD1j0P6dv8cy3SpB3LptT0CqU1EEh8WOHxI6Gy6Te81ygNP0H669nDJ.kvI5LsQi6ognYUISdbkix7lk5e7TsLL_j1sYyCEApJu.B.TLr5MfCA2rOCuaj3QjYnFqG8OymRUs8W8zPhGS2E2KMYRMQjqBjYwDNJpSKq0vrU_R4qCIlDcXmKYMNcqpm_3oYDerHt1AuDT7KFhAXjU4DGFWQ9LeDr11HArC7MSIoExxLQkQqLosBtw4DCWwWnIIcqDQ4M5cw6WRO05I9zdJRgK38w3jWCJ6.tgcx_0iv8J.8B8Ot87UU0P4nlJeQXlYF3bbDX5Wm3h6z4fvI2CuXbW9W4SPkZxvnY1Rrlczuo_n1YNVVilePmf3svdktb4jXPXFliLgl1GdTkjOV8q_OFZzPuSODGq0FDN23N7pDq6zcNliqlZ_Hv9tl4wLnU8UZqQQsVMbVttlxIJk9B9Xp9W__Aq05T21oT74UnQHMPlCcb7l_O81q30_07sTXWqtRLxKa2OGdf8XGDtw4pRkaiTmz4VBg63c.Ap.r0KiubENg0uhQzHfSryLRSI.nrM6VXx6NovO.PjGueFK_SfWe1fnO7xk9h3N7Fiyq_Hh482lSLAVLUvcQ_aBvjHo4ROrOrhFazuVivTCNXyFzgsmx_FcLpAad.Xj1HiffFuiyQbPd.S8Lrq8GT1S9X2xVa1zqekVObRD2rC0HM_tcQkLg3_yj7QfGvpCA3hsSPtT3DVfg_9AWdMPmsPj4lmI0OzEbqLxa.YT12Br3.z4rRM2cgIDDk4b1eLPOl2QU79XqrKz.ssAtEec.1nA"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=92e160d7eadfce16';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, "\/0090.33503?__cf_chl_rt_tk=0KvijhBI1_PtXBuQgI9UgcK5xV6sv1WGEwSAWoiLfxU-1744279028-1.0.1.1-6mJ6QYDgHPQTSxKQjbBDRaogI5bg7go.d_W.kea1F4M" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>