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,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIzMiIgaGVpZ2h0PSIzMiIgZmlsbD0ibm9uZSI+PHBhdGggZmlsbD0iI0IyMEYwMyIgZD0iTTE2IDNhMTMgMTMgMCAxIDAgMTMgMTNBMTMuMDE1IDEzLjAxNSAwIDAgMCAxNiAzbTAgMjRhMTEgMTEgMCAxIDEgMTEtMTEgMTEuMDEgMTEuMDEgMCAwIDEtMTEgMTEiLz48cGF0aCBmaWxsPSIjQjIwRjAzIiBkPSJNMTcuMDM4IDE4LjYxNUgxNC44N0wxNC41NjMgOS41aDIuNzgzem0tMS4wODQgMS40MjdxLjY2IDAgMS4wNTcuMzg4LjQwNy4zODkuNDA3Ljk5NCAwIC41OTYtLjQwNy45ODQtLjM5Ny4zOS0xLjA1Ny4zODktLjY1IDAtMS4wNTYtLjM4OS0uMzk4LS4zODktLjM5OC0uOTg0IDAtLjU5Ny4zOTgtLjk4NS40MDYtLjM5NyAxLjA1Ni0uMzk3Ii8+PC9zdmc+);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: '92eac59aeb54fce6',cH: 'nFWp7D1Ap8UBCyZe1EChfoTlD5zWWRlDymBUAkF17So-1744377527-1.2.1.1-oPQZoSiUBh7O8f37b3nH4COGmUJY6BD6AObF6IGFGzGbYrWO8pSP5ibUcDiGPmGa',cUPMDTk: "\/1251.37006?__cf_chl_tk=srqMcWmgBVlkVZACnABPA8HYa5u8oIXcJ4OeoF4zq0Q-1744377527-1.0.1.1-6wfCIDB_WyPF8Fg1Yg0qss85dLdSAYWsIGBOOuNHO5I",cFPWv: 'b',cITimeS: '1744377527',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported_browser_beacon",fa: "\/1251.37006?__cf_chl_f_tk=srqMcWmgBVlkVZACnABPA8HYa5u8oIXcJ4OeoF4zq0Q-1744377527-1.0.1.1-6wfCIDB_WyPF8Fg1Yg0qss85dLdSAYWsIGBOOuNHO5I",md: ".Vmna.6ENTBm9njom1VfymxMeUTKrrPZ8eeQMvGL1pk-1744377527-1.2.1.1-M9eWo_oJV57tfMtkW07mCgrpVgA1xNcJdsfo0IVozIdWcx2jEngenqFI6vn7LjWfzj4hFYPyUEDJbVgxckDzUqutmLFgLwj7kWDyp2.hzjkgqjZ2m0BIj3AT7gdsBjAEI.3rwCpCLVQP6eu9pkgt9hmbGlQhtMtw5jwBAXM9BNm6EHSP9c_dVRMGWaJ4KD36oIdtfHHjmAo4WG0nlOGhKcNb_ylPKDyTVXsk8jwO0yDfk9nvTjWTvUQD6BoEiSeh7317EC7vPu5hHN3CDHXDh3lsTWF_gcYIoagWk.TRSkw7jeNqavFbN7gj0cRUjiObKrYFdy9IYuEoimyawYVKuDCos2JW14qs_Fg5wX5kvDMKHxYjWkL9BqsuJhxsgfMN3CAznh.6cRThWwSQMir_dKqweMOPGjnk8Y6lvnnXOShPOk6JeFXDIG5Av9c_yOkd.tdDXHPzCwjSKj1zmn4Sbbt9XKENCGT5M.xuFxxZYjulstj5yEci1DfzCk2vUje3XsicvncCLwhVnNppbqdMSV52mXjDxe.e9B5oOah0IrigX67T3M8WNnTnc6E7ms0lne1sZ7WnhKHIK703qJ0YTxfLULaRvPYiN_9hb0jsat36_cjeUtrbyuO7EWNHv0f7Ok9LBVmbFV2nMh1gP2NDG_tB3LlQRTHqTohfXLqwuxvhU4DIY5OfalBXY_0naXBGKFqfSzy9MCOG3yGPH4uCh5irF0VGXtiUnMD2AiCBUELpSRyyBU1mSokIjkGpcy0KlEt5_kmp9ka0g4qTpQZz_14xPTMqphkFgGTpl2mbBVrKHbdbVOzEdmixZr5RJZwrvlawVkc8ZYn2rC5SD0DLii9Hd.j7erRuD0Gw0YnvrphzCTI2xEAfo733GmOIx6rC2TApXi8.btXV.Ee4833moCXEIqguZ3871GsvIqzoV7r_5.mwsjgS61TnnWxQsF5HDxWzEQUDT1Ntb3_35_wBQwu2RA28yN5GZrO.zCuwZpF82Pzxvyni0_9MTKm70NENkAU1X_yf185OJ6Ah9Vd_vlrQE7piIp2r.zN4BKbFLdb_rU7O9bPKn.WMoir55BXWNbjMceT5V41jlf3.9dBIlqjuootTjyGDJHYXKUCJr.TxBUqfRRbOQhsHoX6o2waORdCx9Px89X73yw7wZynyKtJdejMeKnan8jCkAZDrRuNEIXBWuRsjIQ0d_pnU84yw",mdrd: "_p9HvJMnvoIQkjqtm_VtXOeOybqxJTl3hfFbtC0T1wQ-1744377527-1.2.1.1-sSZhtKVbrMCPwUluEN7a2VuLEICIqC01mWYJkeI.c4WArRRSGDEfHhIybOKMlZGfEp5.zDWhQ.1piHUQcEAEi.8x1ChWvonY4lecPQ3E1owyCT45ZvQ4tCYbkvl4ykDu217y9lE0gBHQh74EIbMe_NM1TwklXIFSI9wir8rOvWP9FCDrzhXJV.Z3llT9takxEwkxGXg2P2DEK3bYBPJAsk0JE4qf_GArT4q8YaIh71hfpsFR06ueKOIsxttyE171j6alXI9Ca2jI1pB719YyyBREXE7R3RNUt32Vov0YZR.wTp9bVDW4yHVuImufsfwxbPGsfx0bpPZ_tUEtXwBBLTtXHrw8qkqOg.0VQVOdUeNUfHBMw4kQ3G72Y6DUKsEBqNFGShyUcwngHK3ZP5u5lykUDDmETAArv6FAXwuflczvZEm4r9eqAXheZZmxbR_wx4QkXbdIlXaYc6avJ6zyn_fhszp3ZcouDGIGSiCMDpfRUgoPg37eoN0tOv.RpouCXlTJlJcU_mCiQMNJinLt0gIqkjIRaY7U92U6ZLV8jBLdNnbRq4eIF2nROHN_TD2gCEwQrnz.UJFf0QXyD7lmm8v9KfANQ5VHt74W0LMNJF2kUkG8pYMtERq7V8pM5_WSCYoQZLw.toioDv926lN1CBMIiwzG56YCaSmQEVIbr2xFBk.BSwT1ML28zZeMzafrBzvw_3ZfHIclORPOWTCq4fQDTSwpUKFV14peVALXbIHqotBZ0GP54k8FoZYbddYwe6k.gilc0PIuE90SyTQC93AcN2X5EX.jopzOR108MXanSK0nFtdUVv2_y_Ce2Ik5BBjooapg3Fu99lJA0BQBUpf83s9m.SHqlUFLRNo._D00lCvrWI0TjgSvxne42bF0EFU4Y_mSD7WmTD4Mi1PLl08EIUJsfbeETY.i7jcFFk_543SlpfMJKsq6zOagHO6hpRugnlxHlduaybnUUT57CDXNvQDybxVS85cFCx3zkqJJb_oObNZGP38e3FmGZIf5Z1x1G9Cw9rPRoZYXjo0Hf56i_pKfphyJ1Pwzas4r7m6SETRmXW1T_XaQfOW8fdPqxuKzysWxb4jX6OADTg25Notc6nl_Zp47Th2oy72m3LzX2HEpcaFUw5IbONBlM4qmAvdbRpkr.ZNTMTWqi25BUSRa2NPSXr2K5WHbdNNOMOJBPXyhtpsc7SZubSdE7oCOqPtHEL177kCrb.ZTApjuv2Yv5gyRsqVUdLAG7wck6y3J0pw2SsxdRinfmqbHTy4Ip7PkdjLyc5hIYNpKa1sJv.sy4Jpsa48VH6NxB8aWa2WvIjYPFZFak9v9PwQ8ZS1C64xWT5dlTKcCR3ud3r13XSj2N4w87SUH3bOsiA27WG9aBIVJNBts5x_FCxBt57LDRa7Zp39ljNtOX8CjHLYMdnWFsisk9s6y6k2Vh3Sis5pE5CQlDOptMTtNCev_oVuTkNfIcQOem7uJMBwIx5SRBj.7mhioAjniFbCo8NqoiSULmb9.UQZnIF_yMOIWYHvJit3yAKZaad0vodDqEMSfb8hhf3DJmDdxz_w13RS.5SLDW9KA3qjE2Qw4eGe_X.FmANIYUH2alnRHCUEU7T5rMwRp1u5_._MK_4v.y_GCoDy8Go2uGxnwClxvQU3BJqu9zh2aWKXEEU4sF_J.TY_oIUB4jijqDYZ3XuU3TSySg7Cii0soC4PoacygTv.o37zugIWiRsccu08g5.wUbIKm67CCzXs3pDSPNyepCUAQku83K1Qqj3lAUdybID07aSFWj.DT50ijZKNOmKiJWGRPhOYZXbRYihm2PjXw5dET6cgFpCB4Bpl6gZOXIVR3JA9M5Ma4wDytzIz._r51YcINdc3bHp3Uk.7TV52fuQJPs6DO3cQbB7VI2hrl0HuiDAqqvYckh3ZpL3oM_WvvUr0xuYPr.UwKR8OPIzafHnGBB_Bvv7EemW1abBUtmHLUiNG6nmcIoMiYF_WF9VtQqlXOws6tlsNudaz32AY10UqbCTmLhDqfCooyCaKJE9OodflT3imZn6UqoSZ7gI73CwgYkg"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=92eac59aeb54fce6';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, "\/1251.37006?__cf_chl_rt_tk=srqMcWmgBVlkVZACnABPA8HYa5u8oIXcJ4OeoF4zq0Q-1744377527-1.0.1.1-6wfCIDB_WyPF8Fg1Yg0qss85dLdSAYWsIGBOOuNHO5I" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>