BOOKS OF RtfiDIfGS - PAHO/WHO

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William J. Abernathy and John C. Hershey
SUlppl>se ; prilmiary care acilities (or ueniters) r'e [O ebc located in the area. WVe
dein,. dist:aince betiwveen two points it tihe ar'a tis the rertangular .separltion It ll,.
iumni of the vertit.al arid hlorizonital distanees) betwee¡n the tswo points. Thir is
,'nlr. Iiit inorf rl valid l1h:.i Ihle dirret, distani e I)\ !we', 1lw twvo pointis. siart, i¡
¡livitidualsl -will tr:ivel iiglh\\tways i tihe tegelmr l per value of the power hlas iol Iue)ct empirically establisheid ior
the general eaise, and various valued are reported.1"`1 The present formulation assumes
a power of 1 for simplicity. The numerical method used for assignting fatilities
to locations places no constraints on the use of different values, should they 1íe
appropriate for a particular application.
Wlhen more tllha osne renter is included withit a planieitg region, tlie ¡ormula tion
inust be extended to recognizc the effect of distane on bioth the user's choice of a
parti'ular ceiter among those available and the chalinge iii overal3 utilization thiatl
r.sults wh(.n nu,'iío crínte í lrs ar: availal>l. 'l'lu .ecffet ofl distac, oa"c it" iliza.ioa i. bIt t
meswured iii term.t of the proximity to thie clo.sest ceniter. ''lhe nminimunim dist:ilíec
from a cen sus block i to a center is defined as bi niln,-i, ... .. b,,.
A us.r's choice of a particular cente.r from among tliose availaltle is stron gly i¡iflueticed
by tlhe proximnity of the cent.er to the use'r i rlatioí to til, proximit y ofC
* tilher :',.te.rs. Rtece!int re.s.arcrh by the presi.nt tiittlLíori sh,o' tsli.it a regressjim liiO