CINXE.COM
Just a moment...
<!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: '913497a56984f938',cH: 'tarNB65Cs1EJIgv9halznZC4drvcCge2ItDD_GcJ4EA-1739782882-1.2.1.1-ZE8F1fSYH5CJc2BfhwWue58UHed6CFgAGYp4Us0RJZqcgbamTDXgNERhSdTvnRGv',cUPMDTk: "\/10013126\/harvard?__cf_chl_tk=pAS.F.VVVoVQDb2pX3.gTMj4UDHhKKncg98Vf44SbwI-1739782882-1.0.1.1-3X1mQaNcxdL3IlkibG52rDE_2YfDl7Xpb8uHAccA7m8",cFPWv: 'b',cITimeS: '1739782882',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/10013126\/harvard?__cf_chl_f_tk=pAS.F.VVVoVQDb2pX3.gTMj4UDHhKKncg98Vf44SbwI-1739782882-1.0.1.1-3X1mQaNcxdL3IlkibG52rDE_2YfDl7Xpb8uHAccA7m8",md: "vZOtxc2TUnUErKsLZOi_Cd5rX5r_Kcu0IYU1a2jtaGU-1739782882-1.2.1.1-95TTFpj.GtbKFFLBL_VZG44v6oh2lYHUyW3Mmdsj3jLXWs.qJQxYP3nrGhMQineJr4rkMx08JgGJHbJUAA7vPI.j6SUIHnWhr9fcctvUcEk99OA_vACC_krFmLDTlMHj2yGtuPYuv5_YIyuYO1AvmMhuQPjEinqxlaRY5rvjf32aFxMeFfH7ze_Tpy3N9of_5hyepmJaCQOpFIH7H4HGD1dDuGtZmy7MwlzrKKtBMxhYcprCcfCsxrh1Zx7Iif1KQUH.fpkwHgFnZ_EE.Xar2FmUGMiF2LgRJzthqnYCgpyeN4K4KKl03CVD.FRFIfiAid_N8e2ml0d4X5b8a.J_FP88t4r7rVJ0TqpXxBWlTAPD38AoAj.k4gfhBdLbrP0Z29n.cYxgjeIbbxvR847tL6wijhah4iWVgEorBxvcXXDUx2TOkPU.fWYsmSU2bU9qIn68Ayr9XsA4FD.Ua2gbrgNTOQQT6kGJtOnZ3mUIX5UaMxNJ1_A27.hjTCXrGQ0lKA6nlJ9HvDh8YVU.kjfGr5yfcrrAl7ALtK4RPetqvdhFEvBtgcrZ6.6NKbPbQKhpDR_gXUKsRTULXZ8DunL3xgge4eBAfT2LyZSqd2WClW2B90syo3vjLxlTpaUSRSiJBMQjA3TPDKEnYfUs0VnKKcJr7gFBuSbx125yAyI2evSIWyhum4QnnpBx3iWuXM4dUZOPkq7w1EqfY7Hy1K4oNdcl1qBaTt0b.geuLH.vft8KkOX2S2ZaPVJj6pWKJAr5YT9bzm4WHpzM9a8yE3ZWjGJIIr0crSHpbzrPtoLqaq3NlAqciwkbBMkYz5wvNQwjqoXoly25sjV15ljCLjKgaB4Q87hHJji3g3oZE0UKRZU9mX_d811S2ORKrygRT.a20HMdf_SfxejtGgPy.2or1.v4qBo0iU4FiSQwV2OGwq10S38mi_6Gu4uwlabOwpvckLeM1C81UZNOY.jtsu6iGDUrv8cMR05qpmpP615ZOpd5pMpu9Fkd_AS4Nor6yItf2apTPBJGN425q.bsyErE2sm1C.T8Tvlq0XqALI8o8uOZMdOEGdh5qDM3e7Icrt1m3XzMMa1yE0biArtMOOeH5iTfkybh1P53bji39_UACoiyEM.rBspWbGcIOEe9oRIuwDMKNUxTznViiIxI7jgmW6GNXCMdZ5mkgCFbHb5heJbEfrcHUnAOK92LJahqiGlTtKMpEG1JFOyOar74Jf1IOhlD27aO8Zc21YviwW8ccRn115nynC9fhlHyxGTUizH2xUSAHoDg_7qSVl9TnAEeLeoFB6Q2nU4p0sQOuLdQ7NZ2sIquaIJyTJNJfMAEvPUkjlZhk8nL3rxK2uaoHUy.D7SZ7qnaXg0n4tKxjLZawgyhDs9ULrUi24Xt0_o6bcWcTJHYCG9kjcrlIVwON.c.seZX025TXbNF1a0._._PWtyx_J1BIevx3gGr1ESsIJX5BvNjk.naZFggc6uhmY0B31J8EX96KmHpQ7_.DfnXZ4NXdnrSx3khP6UdkJCi5svfyZsTe.Vqx2U6UYMyw08FoGKFrBVf3V4dt916VSnGUCd2NK_gmhzj1hqBAp66Si_AoQiZiWzfC0N5sMl2U6BrUwsCD26MLtTMKGTHR4Mt13PXLPRKhk8sVEuJvLZX3a5hGZMPCenbTIOIyaYB0Y1_IKED38i99nAV9jmNnB7A_Y_QGkpdSYcUdZ8R9y4NUjqWcpM6JzvbPWgwmkzqybYmB0TLZpGzsFoLL9Q8uVCnCVoMVtSl1RoP6pS0mp9Hf9H7QZHijYcVriW2ZxIk6hBmrDI5fQ4UXPK5sKUpm93xQySV8A991PZ.KLaexnxdGhRnzxitNLCJPdSNUDk6qFEtTdNUIsacZH48xJvpJ_A3RKQ",mdrd: "zCIij6Ov3R8_zJMC0YvRKSI3RTtQfXYGcCgWJFTmLoI-1739782882-1.2.1.1-2jZ4wYiqHX1v3MbbTjZ1FtlEpo.53WJwLApvEKqN6zXfLqPHa_4fkZwxNlXDKf1YuKj08SjhMJHO0MiHo4nmR6bMhAKqkPL9LMu.ZbBC_7kV7Q0cn43hF7I9GRTqRcfiKJDpd_KGlsteiCL2PU8qJTyMJkL.6C2YqQVBFZUbi0VYujbprVvN21mnvSnF3HcK7cv4BTQbGwcS0vYQuuUyKyH2d9tyPmHj14w4BJqlXN9DR7uXzBaNuJcTchv.ZCVPIhJFf5a_6a6niZds_azZ5dSM7oC0wgAobs8KDf9PvewJ42W0IaPwL58uzAsWumMF_un7YvRFA99z_Frn2ThAYW2YQoauToJjT1UkhWN3QL9pGmymiKU6nBrhKpxVOvtSPdxUvi7wq0sEJedLsJMoeSkUVvQ5U.OGRw93L6Q9NcRq.bcM549MAWNEhIJgXgZZ.hEazznkOzvxoAtUIPTALPpNMf2K7Zkvoa9oSa9C4JOJJVudZk_S_0E0brnoRpAPkiapdHov_rVKP.sZFew3yMu8KfWiipxSG2SNcelm.sFvyCQq5zvYZF8M0xp.jDIDzBzKgjt9Czqy8b024ggkrTyEU6rTRbc66Rd7FNBJZstRZ9pjHNpnsvuXb4b5v.n6C_xJFzZKGMFkBqc7gTpn.GKI3KkfB_6rJO4VPRdmOdx7BhiFSdT0FR_kv7C82ZhV6yqXUYBlVjgEJS3qSf4TkMMCfseLwZv.Ew_dndmd_NY5u11puNjfp1Zkytawue2RgTlFVtD0c4yg_WUgnU2ykIpLK5fe1IUC3l1S4143Q5IMkKInm.sM725eLPvE7mIBTiuFNt8rv9.3f0nnQz8MIBpFcQopZzzxAMDZosy9hOgw9lLWWqqR_yvwM.RN2eteiA3mMyrCN9L3CraEtDR6sRxcJ3rsZNYzy31N3yLFNc3cesQDU7N7YrHDI9mDvn8H52vj17deidagYaEwkLyiBdxZ79_RVSCOF1fFyrEllBB5PeExyanu2.CzB_fhNwwr701uItsAfR_OxzxUENon1zlKKyzvTq3p_fe3pPe1yMv.5JoQZXxKibjswvmdsu9Tm9aaHYLhPSKrJVzheJD0Fthz2tbFk6LKEnGbc_fPE2YtchxvOQJLT8fGUfbrjD0MvbQwlunCBj.rzKMWjeRd2UdVtgbwnZ0G4HgtQxz0ZwMEHehORlCEk3716ptZUS.ytw_TfBn4i623TvUZZYdFEOtqOFDLINinz4PJdofZZnbUQzkHNiEoRQKvzltLH12YLCxHE8IJ0ebgt09A01r9bzJtD0Tx4Fb7hMu4.SP6hGFTp11hlCDoKaaS1m1sjnyE9zXMNu5PJWtDLnTeQcd2v.6b5ZrBPDvVmB5TBM3a2tcyyvZ7hx0cZRlH6i7laMFkSgHgveIv6ADr3Lm0AB_3IWO0gfZI5XjihVTAF_eC1gNOwF4xnNc7dmQcWhX683j3cnQMhZq.klfLmNottC84ISWfo21qzIYvruhdSGAmm5x9yindNU22bUDI4Pnbp.Fterz4J2V85Z3UA19AtUZF.QFZenqXtL1EH18oZII3qI6y9NPNijY4aLuA5VbCmUEUC0i6CeJsPN6.40RfKKSdSuD7U2g9mLayyIXm6O5YtIgzYfN7ti49HNiqh1V1ZvdyStQx0xUEafhot.nc3P4HdC4b1TIhRXMg7zIj9cb.8x3dsr0It23l0YnCAQqG_4dQKiglMxftAvPfEJGWjYCwkEGn.eBPfQznNXp87uz4j5XNatFd_H40xhC3gQNICBHOL5pdd5ywpuqZGl3LSlL7ssSavYyuRujnmbNJE00WK7cQh4RcFzLtpOo7k1VItWNjg4moCpT0ZN7lPES1fXbersMDzfpt0xNiM.X06D3RJzg6NHeYb61DvlMrqRoT1WKt8XSjjQNd8x0vZb.oCBRCNRGFZ64wQsXrFj20IRdr599XlhPFS1dCJAiL_e.Jdxi9qAKKBFj9QCNgAEdpnMBJeQ"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=913497a56984f938';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, "\/10013126\/harvard?__cf_chl_rt_tk=pAS.F.VVVoVQDb2pX3.gTMj4UDHhKKncg98Vf44SbwI-1739782882-1.0.1.1-3X1mQaNcxdL3IlkibG52rDE_2YfDl7Xpb8uHAccA7m8" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>