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="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: "www.gsd.harvard.edu",cType: 'managed',cRay: '92eb1b903daea066',cH: '0MzwU8eHFYJzAWSqM3b1urVz0NaGggac63iK2ztmnOM-1744381048-1.2.1.1-JQg9.oqJfUsPd1M06.0yrs4lwrl3FLnEZ1luYyBvVtreYssRrMdGsMWAOflCT1oa',cUPMDTk: "\/covid19\/?__cf_chl_tk=6hzjAV5w.mB_lZDRs9fy2P0cs2j5SOKhJZc.JSaI3qw-1744381048-1.0.1.1-GXzv2Lsd8RRRqhZGuBkUs2HOcmgQNSh9039d4s2UoPI",cFPWv: 'b',cITimeS: '1744381048',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported_browser_beacon",fa: "\/covid19\/?__cf_chl_f_tk=6hzjAV5w.mB_lZDRs9fy2P0cs2j5SOKhJZc.JSaI3qw-1744381048-1.0.1.1-GXzv2Lsd8RRRqhZGuBkUs2HOcmgQNSh9039d4s2UoPI",md: "iFcffDA6FMg0HDtPeOSDtaWy2jJYbygsUDPaOuDwxCA-1744381048-1.2.1.1-TwDPWOfJ7mGE8zk7cgP3T3z9HeRdRe_j3v0zzef_j6IH810h6t3.mgpuJ4Wz64ZgIcAQ7rS.h6u1UrSpYg8j0MEkOyrR1tzlhd7KI9djm1lABDnK.kxAiBBfbV0B5PBNAKKR9ozLPwEHrF7eVgjVKVOeIO0Liq288GDimtnZMJC9d1LNEz.pmpNzlq4HS_pFekihQnx274FwCyCbc0TFhYAzuB1TmcKr1kP.8XW7MnTxiyi_QKwJRaY4ivDq9913CloDpGFqAjWkmQs36Ihdbb_C428VoewoJNqKd.eAoLQ9LHMkTiCT2D5mweaQf2EEri4AJyW89nUyUTKk1VCcoi5LLzh8XNqX0fF6q0purarVEKoACgTH9REMOegj1Q7coSG7lez.RKuHyo23ePhCIq2kbgCofWXQGBbKiJhUlBviC5w4Z_vwVfdabc6MZLtCOCd.dnj1Vqp9U4IRN5RSWB5ya1wfSJhgZ9vC.aPccfJtxt7SAXRP0EKim3HIYP87Eyx9Be1WomeLRvkyOB_Bv3Ij00HcmjW4M3iySpRObkCDemS80R5ABFlM5mtayP8Av4ot1fPSTPMAar_PUscT1rysbekbYgM_20Hp74N4bqN9hp0Vs5mvQq0knBkTktVyNLjmyfjRggIFgTGFQyHILKkztMRIwhwIkEf2n1uf34Zfo3mkzbMnMsd8xAX9quGTm6PsEB2WhwyutPGJe2cMs6DGb7mQ.FOY6u_rNlQbVeXf8i.kNn9MukyagPtewN8Bunt83bpVXpYDk.IoMgZM4HHN9iTm3TRD0PBBc4uahOuHTUNz6aW4QfH9eL7QLVg3KIfORhzybzMyCMkXLNigc0uD4yasP4vhvI4WEH0ORHwGjhw4my70j46wcOzf0M4PaeWQGjHvrp8_zTo7yGjBU.VrrUwb4fU9KYrHL8ogOWuTyvtmh.TU1nH1Kl3QCSeaEqgFTI6Iocfk1TCvC_azvw98SbtomTqsn8foer3Ys5K7iwScS3p22lgIF8ur650vz9q0ZS4nwg9EAvlleKuO_7OVNEp3MCL9wB.LIkIVY8hr140w8RKD4bmI9aWxgqQtrBd5.K79Um1l_HUtNNdZ1aiEDBX757CSLsRzvlgWvH1FXCzpNcjgsP7IaQPluZJQWbLltezVujGtqMeOibg9Vc59gRj9imIartmxjXWMc_vW__aFXb6joPOPgP_vkAe.WIZp390a5n2lCjQ7jjN1zaaHcceHjyg7FleArr84BHk",mdrd: "8YYDnaeemZiIRhUxB6DNjHaLeE_tIa94VsyvBF8vSwM-1744381048-1.2.1.1-EwMSjeNr_MSPb4yqRTKHWVuTKMO7kJMmD009YSbu0CmH2..ylSWbAee08PCLZQlRauz92fd.EGyjqjcJAv8fzD..SLm2Vm0BiYaa.el9lDWpViUFlYpjqDdZiFgUm94t.g4H9rbgtZuNvEnVmvPngaWpcz4YufnnGI2cwQI3Pt9fjvCLwKDEGsmXco881Nl6y8LPJ.MZomjcHC9W2zK.UEknCpqiFAcGVK.L8nE8.0bVquC8yxNEklHOVIyD0Pg6_eWdat6cCE8tun2Cj3.Q2mNosq.5cWMgbNeRohuYBXgMfF1sYxi9yg9mO5TFKeUPZ28pwstXY589_9guyYFcnGH8cB4bFvVmgPc2WEBSyUNaouIW2dQYErYs8Qz4lJ1pwwzf7vBFE5tKE.p2NpU6vtwBZmS10SmhiEe5IkmJWbtjedzO2h5JgQN6S5xSqJerI9IcWocs2TedkQhxXgiVB8FsF4ngB7h01VJ7Yh_qLLTrDfvOl80KzpekF.KW_I9KVs7yh.CddrTJ2tXDVTKVQRI_yRk19REtnqP9KsLhKD4ZUV901uEaknQDxtD1CJS9MEBN.JjX1gDgnRTe1.SaforuVgX_AQbAEpVVTDmmjyygOw9fd2ig1Lx3SpT9JCRH9g6mwpy_Vf1h8VkBatGRK7FDTe3rsZQTnLFvf_xaa40GQnZGaqSxfDuP4LGA4Krpq37ZUB3LRz750mIjGkeHsdd.MKPc_XaB2jp3W85cabvYF_sbcVrN5EFi7WeNXS6YFNuXTFiWOiQLFJpRa8_4ryrzBiHrvoMrGDCPN8uvgUdTQeeKo7vSATTO0bkxCJ6v3x11RsbM8rNODP62weYIJch4WAZXlQ8JjF5K.vXZeJLqAvEarx3nlO4wInVA5H7CK8K8z2s2cbbjvfwx_Tt_BkVvO.XWcWK5PIWwAhl2NoCc4KV_8MPfLY949aM3Ocmwba198vsa7lplFa7dxVBj0C5ZK4RW9ghy6ebJTF0027kdRdK51kdQIwz3nfT0lpT_0G.CJDZDsBOdkB2O_PvpdPU0fFq2Y3i5dxHFTIqIewYrQsaYgvCAzw9cBcAkY0uwSvLhGH24.Wl5_1kX.lDVfSkL7KURsQI0jxIbHcHGg0mWkL.E4HVkl4jVjsIvWHlITzMlo4DTkpcwAC3eYBiDlObHoygxg8LlU.ayaH5KQEuLnxGpr2Fz.3Kfjh47tr6Y.G7inzfCTuRdaV.oOW51GGTfEZqvHfGbdgpp2C3kAUBDh6q6A28PFzk5oEHlGgl3hFSIWajl1a6BweARPH_6finBFTtIGIhse4ZvxDF7KUYUv31zOzCn.7Zmgto2ly6b_g3IDB4j9jRgGd7jQAtQcTVOAZ5IzQ.eJiWlweYZOF9_h7V9jz1eoVDbt9.MNACXptbL3qCjKLPkpLhNNw9TvTQXRBzG14TH9fywt8J.fPrfFoYh8RrUdFtrpgoyDoZRVdK43_hQ4SetrELShl5bCi9b7JPSzn90a8JnXlek3bJ9fVFgcUt5siHmlVeF_4vtxCOO9JPi6t53QUmPH5gfRVsi3KMXn3u8.DiVPQeg3fTNUE0km9Uwaor35XBrHO5yTS5nv_6lAeztX._VaenQOx.uHaGq0VyPgc57B0TnNtNVRUYFZO6rOElja7mHFONQo1cHdMYKmdlKL0.6BXL2wiq1dFsKBY.on8vFSuwDOeECr4r9w20JiAyjDKiIQnR3C6xTDyrpRnWra9IC00pUHIl3dzebwpZXlH62cqK0eHmS6kWDogBrgqlKgE5JATC5L675jkwW5hAFn6lMEZlFtMk40TV_.._TRvL_kNxOPFguoBeU82dyUWaP3d.nqQ4l7AfSYK2wPO9jAmSRKqCEmb.ZbZkeuFS3xlFXXj9.SbKYZsm__R8gOfbBJQ7xRWuBoNQtyhvsYnRNlnJhA2MRIIpGDXLXFmPrWZ4Cd4TBYjkcQeSL9yXAoohrQh5WWtEsQwZk7OLONCsOahBCGHt4jkB5NmELchB.E8IkfegrJ.L4QNKW5MPkXL2i4kdRS5b1nktSTDOlXtdIa9PLSZmLcYilZQKql1eOdVGLcMcAAI0"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=92eb1b903daea066';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, "\/covid19\/?__cf_chl_rt_tk=6hzjAV5w.mB_lZDRs9fy2P0cs2j5SOKhJZc.JSaI3qw-1744381048-1.0.1.1-GXzv2Lsd8RRRqhZGuBkUs2HOcmgQNSh9039d4s2UoPI" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>