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="120"></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: "publications.waset.org",cType: 'non-interactive',cRay: '913424f17e6fce41',cH: 'D_Y2pi1o3ZdWc_iV_EegRCPTObzJo.BqkJGVy8DyeR0-1739778183-1.2.1.1-hnSZQGLaSKFidNtfdi9yv5BrczskL8vSOK8JDptr2XFkhVeYJXUodO3vQYPg0LkF',cUPMDTk: "\/10013861\/harvard?__cf_chl_tk=thqv4NcW6OSuDt0lNk3Z3rRgshrAqe8MrbiSZHR..vE-1739778183-1.0.1.1-MBVZpAKi5uD2vKwB6d6Tb6I7B4h_X.YCgSmN.3iSEF4",cFPWv: 'b',cITimeS: '1739778183',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/10013861\/harvard?__cf_chl_f_tk=thqv4NcW6OSuDt0lNk3Z3rRgshrAqe8MrbiSZHR..vE-1739778183-1.0.1.1-MBVZpAKi5uD2vKwB6d6Tb6I7B4h_X.YCgSmN.3iSEF4",md: "k3piAj0lmPXBLaGFjG_H_rcRthX3DLy_PuGcnCBtPDs-1739778183-1.2.1.1-iAm30P_qm3oq_JkAP2ifGsgj53jdF27QTg.fVUG3jwtIY9bjFhCPNraY.tfk7B9AQjMWnH25MbFoLeQ5nQClOfB6FLS2FCQiDEiPSRgcEqD7gfJx6.1X_Li7xHn11IGw_v3GF33bTGbis.FaUXL4mjSICg.yrXTpUIsa5xNb.CuQEOWgO7QWpRAmdhhwg8R918kGOCLljcQmViqP4gXAJMsFjy07Az71axi66O_VyeFdHrtuWDU6K7Tume0v3oR1rRoADlf42iGl2oKeASYA8iQ9FEwKVPrrHfEU4UaqB7ygJS81XkYhnams5qvdzpIqQXJ0EolvQv8AFbOyfjCxTT5rMM_X_sga_kE7hmS5FV7G38gMc7M3fynRSjdJyhkoIWrQCrO_bRbpp955Ypwa38vQ7XTed0Z32SWgJ7C_nXXwjrD9IgOv0dwqAVAGqR9lMuT_8QiFTWGpxyok9BnMsi2rtbnRcZwZwVDTzCLK3mhtWremI_9pMcs8Tdg5SKGymWgCFttTx1Expv7pyb7oSyjC0XtAXRJsTL1idk.C6QiFzX7hY.BRRkWMgXrB0YjFicdc7voD.3QwUVemYHl1Ba_pbuEd_ks0sODc9Ofk4mZzw.YbhEGsw2LWzXpjiTZKuy8F2V6J7Du8lKEK4xPzXhFtYp4kgVmTVqWtxZ266HyKjyOGmLeJvD9KdmOSGRHnQoxqLVoQnKT1c2KxdqSCygmS8OsmWW4e4dYtbdxYSBjzj.zxmsiJL4afWPj.hrrJ17CIp2AHYqv6r634qzDV0LRvN6.b4Fkwbt3eujtrLTjfmP_FgJZMCuHMKKFPFW1dMhvcnWPyHeX86z6WRnH4.PFZBCoMqCmwR.KsgPrTfSATsqr0MzdZmBVMMbKuAaUgakhu3FpdvbPBRz0t1rcfMJR2AG9QPi_1RUY7PBZoxZaz_HObIoedKAphj2bJgl3m.ftIzUeEcjlmaHXLsEpxIkkHhrB61DhjEUkax.IiT9SUiYYVaQUWaClL3ChYkOLYmLCAjlhsF4LXUQQenmYECpxVvE4htuRkE8ZWRdt3QZSBjURdvhYa6WJrlqANzbGB10BjxrQXJZzq8dClSM.exuhWAZUsUW.SjFIO4YECeJrxculjyfGzJ4NboScVSs6s8y8crd4fwOaZkFJy9CEOt8VUGRTOnuch813wi282KZ3hP2zum9m3TdEJ6ZPeA8z51XnGywP.OUA8snXff9gFx2u5KG6dzJ1.0osXvUaaqaKLAgrcd62Gd1EDTQAhYwTz2T_M68dzPwNhGqni5grbBpcf7Kwxq.MbCSMcF3fO.YXP5KuwGgRJ_2vCeC0LtcGRDfV7guCTuNZZI1sFsats_4kiILm2bpNTyn7mcnKmRQ59ai2IMa_AspZrd0KRyrjSkigyalRvKCcvwYW3WoJ2uoxzDJbsojM5HNG_XbvWZh0tPYkSEtjNu2kzw2NZG2xIRNbvjPUKLG046oAsgRPeyfNdGkpU36wRaSlb7WGPAQAGbZlsnplXJ_HFgLeSgSj_BrYf0Glw9blixO85_6spCSJgf.yq9Dme4I_.NMKvHh5O9Jskg9pi97bQ4eW27.Hk4_2R8STu1jQy67jkj1q2jCu5GN65OusKnJs0zg_a01_nqI1se6GKXTh3uog5t9QYbKnZ_NsqcIbqLRnOjwFixu0.uyqzZgLBW5Os5HgNgJB8cCkpGcTF2IoGIdC6W3i7U0_RaBAhBcYw6gRzM.weaEgMLrA2Ref4B7zWELTGArvjy1es3kCLRdM2gSlpGDK8Sz706ls98SDuiEYfW.fNOT9_DHcNE2Nw1g8SX_sFPdvdbPAAL6X88DCM5z5eMI7aTE.gEMUebcqYSGTwGUGKlJ_SqeNbf500p5nPBPyl5po",mdrd: "iv1BU6e6NOUc6KfS2R.tUhbApIQGjIKV49xeBP4cx8g-1739778183-1.2.1.1-W1EhaAn_u4PsrycAjq1zcDwgqVWGcgutCbPtjLHp2E1nISJbZI9LKJWPy3gWFlNywCkKR_wwyMQhht9xSDJWWhdrvhwPmBDzx0oE9r8ibuyQhuPBcikgGmmWVcNhSnmA2AMJsfg3l0YxUOQ0c3ElJ3vgzFXnXUxQMes6YVBPXtJwPfC7FGQ6nGTNP2WNrx1Y9Cfp74jIJH3tuyqMRzeFbA0DtQRjCYGmq.ATfajvNXpYpkWZqC0E66sIj3SBJgMSSvhMy01JpAMgnpJN3UP7V9tp2UGx4_uy0QfZEFgei7MtgbF2Ym757SfPcIA5XBEjvgrco9ZOpJr40pxUT5BGUEKARElaT2gHIF9QOy4bn1NzDw0FAl.VzQBu8XpUqJNbSx1e7YhPJ9jI2u026OQzBAO0eWDh2NG5Youviac3ZVl8Zua8yU9NBVKjPnUdoYJy9COFdWlVzbw0HepCy9c5EzguOQcALDJI7jBtLUY4s9KzWuDJOoLEmHPcK9Ux.hWucRjWvKEWxYCUBUC4rzyt4XTbxA3r4pq2bZ5BX293tWhxRQtnTAoFm15a9268YibyXWFGqZvjnz1oWTKBOJqVwToY6bF26oyyrslKdNQdHvQ.bbC0_t_n72fDodJaPoW8vKG9OtJN2k8XjV3V6djESnU.AH633ERFKwiv56Zmy78p9KrFdscvPxPA.oET_PRjNKMzmqZLBSidGpNs5JdpLt2hA8NkHq7DkUYQQAl0wwujhcZ2lv.bzEgNB.hexscEt8WIuuloVm.IKZn466XtoRezt8h.OMPwFUzTkZ3wHxK2z8Fud_2JMvcdq.h.PAx_cW4L42PzcHrDbfFYaYPlWbozvAUfUF3A_eXRyY5aJK1U6YjexKTDDjODmqqfyDh18CRqNl0u0aRw34dY4jyZdyrintSlRBeBjyxInLnW_i.YJLjYyBIszHSVwBL21Gd4kJqNonNY2ow0FOXzKouRknHXrTteS5BsL0rcLZV2JWMnVa1PqgdaRJghKrnWzs1jE5xGMScQWpqFAq_wfTqJUn_kQlLX9LzkDr11GBhZUxcrjpoHfNPsOOM3UtmkIuMi2bj8R6tBEPQ0.LVtdn624UFEC_fGu.GjDZrpIMUsl4j1jNlbSmlP.CcW44pqhspgoAblQHYtKfjPv60UApelITFgfcUbcp0d6quQmo3dTgwBlRBUbEM4t_kKP8ZlTIjnZ7QVFKu6onMKxqHxOoQ6ifThi99d7MrmuC_Wrd3iy4k130hWQUfFpPNbRL7iyoO8cAzhl5QYhfseNJnxM1ZKjG4KdgOmxU_p7xM_dj35giGiid5ZgdxbYIJxIPy0cIAf2N9ItWQzH3Mvt1xXYZLBFmZu7m.YcF8VGxJNRkCwX7LRjnrBOtNV3nGy9ZUov8xAWmNt_bn.STUM1_KiV79mtC8emk0rvqJwGIm5TeuScrtPJIY5XUOEkSWFua0X8sesnTWyatpkCTCrzSQt5RJ6hcJXwjNV3Wy30_2E1WuVdN4SyVN2EOlCBxIAmLeqnJVQilJzdE.dcdV2OAR9O8d19QL4v6KYCGbEAjX51OLh3nVXM9fABwOjx8bpkoC7FGLgnO_EEWRsuzqCJwVqlHVLAphu9g8z.jdRtF_0050d0VauOkKsIpY1Qv3J0etgKeuSaa05GHi0mK2v5NGp3Ccr3h5VQoWdzGBFgSwhgg0yLGTElKXmSTH0iURlt5aj3wFWoAoGJgHveKPtzLpre.74Av8_.GVfxvSPnCXfxoqq80aAtNu_BwFo1eRRRfmy.l8eM678BFwNg4eG4yatLo32FElp.XYOoVITPZ45D6jTyVSDBWdXISKlSd7UzOnNGfdLdj7yFnnjF1Ttg3PPHYwmYjRGPlkvKutvqNl6cRhEI9GgUhm_0rPmqgxalo.ckQqKPbfRLX5gNuMY7HX6wZnFhCV.TMsChRcn0AgLlOTvIDIGPqxhaM4MAUnPF4GWvA_FFQCcf2oxbMdWYdnnCYqnqg"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=913424f17e6fce41';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, "\/10013861\/harvard?__cf_chl_rt_tk=thqv4NcW6OSuDt0lNk3Z3rRgshrAqe8MrbiSZHR..vE-1739778183-1.0.1.1-MBVZpAKi5uD2vKwB6d6Tb6I7B4h_X.YCgSmN.3iSEF4" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>