The refrain is at
http://gregobase.selapa.net/chant.php?id=3038

Sure. Well, at least you can copy the GABC from there, and build on it to make the complete version.

Here are the Psalm verses in GABC (thanks to the Psalm Tone Too) - Tonus Perigrinusl:

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(c4)1. Mi(ixhi)se(h)ré(h)re(g) me(ixi)i(h) De(g)us,(f.) \greheightstar(:) se(g)cún(g)dum(g) ma(g)gnam(g) mi(g)se(g)ri(g)cór(g)di(g)am(d) tu(f)am.(ed..) (::)
2. Et(h) se(h)cún(h)dum(h) mul(h)ti(h)tú(h)di(h)nem(h) mi(h)se(h)ra(h)ti(h)ó(g)num(ixi) tu(h)á(g)rum,(f.) \greheightstar(:) de(g)le(g) in(g)i(g)qui(g)tá(g)tem(d) me(f)am.(ed..) (::)
3. Am(h)pli(h)us(h) la(h)va(h) me(h) ab(h) in(h)i(h)qui(g)tá(ixi)te(h) me(g)a :(f.) \greheightstar(:) et(g) a(g) pec(g)cá(g)to(g) me(g)o(d) mun(f)da(f) me.(ed..) (::)
4. Quó(h)ni(h)am(h) in(h)i(h)qui(h)tá(h)tem(h) me(h)am(h) e(g)go(ixi) co(h)gnó(g)sco :(f.) \greheightstar(:) et(g) pec(g)cá(g)tum(g) me(g)um(g) con(g)tra(g) me(g) est(d) sem(f)per.(ed..) (::)
5. Ti(h)bi(h) so(h)li(h) pec(h)cá(h)vi,(h) et(h) ma(h)lum(h) co(g)ram(ixi) te(h) fe(g)ci :(f.) \greheightstar(:) ut(g) ju(g)sti(g)fi(g)cé(g)ris(g) in(g) ser(g)mó(g)ni(g)bus(g) tu(g)is,(g) et(g) vin(g)cas(g) cum(g) ju(g)di(d)cá(f)ris.(ed..) (::)
6. Ec(h)ce(h) e(h)nim(h) in(h) in(h)i(h)qui(h)tá(h)ti(g)bus(ixi) con(h)cép(g)tus(f) sum :(f.) \greheightstar(:) et(g) in(g) pec(g)cá(g)tis(g) con(g)cé(g)pit(g) me(g) ma(g)ter(d) me(f)a.(ed..) (::)
7. Ec(h)ce(h) e(h)nim(h) ve(h)ri(h)tá(h)tem(g) di(ixi)le(h)xí(g)sti :(f.) \greheightstar(:) in(g)cér(g)ta(g) et(g) oc(g)cúl(g)ta(g) sa(g)pi(g)én(g)ti(g)æ(g) tu(g)æ(g) ma(g)ni(g)fe(g)stá(g)sti(d) mi(f)hi.(ed..) (::)
8. A(h)spér(h)ges(h) me(h) hys(h)só(h)po,(g) et(ixi) mun(h)dá(g)bor :(f.) \greheightstar(:) la(g)vá(g)bis(g) me,(g) et(g) su(g)per(g) ni(g)vem(g) de(g)al(d)bá(f)bor.(ed..) (::)
9. Au(h)dí(h)tu(h)i(h) me(h)o(h) da(h)bis(h) gáu(h)di(h)um(g) et(ixi) læ(h)tí(g)ti(f)am :(f.) \greheightstar(:) et(g) ex(g)sul(g)tá(g)bunt(g) os(g)sa(g) hu(g)mi(g)li(d)á(f)ta.(ed..) (::)
10. A(h)vér(h)te(h) fá(h)ci(h)em(h) tu(h)am(h) a(h) pec(g)cá(ixi)tis(h) me(g)is :(f.) \greheightstar(:) et(g) om(g)nes(g) in(g)i(g)qui(g)tá(g)tes(g) me(g)as(d) de(f)le.(ed..) (::)
11. Cor(h) mun(h)dum(h) cre(h)a(g) in(ixi) me,(h) De(g)us :(f.) \greheightstar(:) et(g) spí(g)ri(g)tum(g) re(g)ctum(g) ín(g)no(g)va(g) in(g) vi(g)scé(g)ri(g)bus(d) me(f)is.(ed..) (::)
12. Ne(h) pro(h)jí(h)ci(h)as(h) me(h) a(h) fá(g)ci(ixi)e(h) tu(g)a :(f.) \greheightstar(:) et(g) spí(g)ri(g)tum(g) san(g)ctum(g) tu(g)um(g) ne(g) áu(g)fe(g)ras(d) a(f) me.(ed..) (::)
13. Red(h)de(h) mi(h)hi(h) læ(h)tí(h)ti(h)am(h) sa(h)lu(g)tá(ixi)ris(h) tu(g)i :(f.) \greheightstar(:) et(g) spí(g)ri(g)tu(g) prin(g)ci(g)pá(g)li(g) con(d)fír(f)ma(f) me.(ed..) (::)
14. Do(h)cé(h)bo(h) in(h)í(h)quos(g) vi(ixi)as(h) tu(g)as :(f.) \greheightstar(:) et(g) ím(g)pi(g)i(g) ad(g) te(g) con(g)ver(d)tén(f)tur.(ed..) (::)
15. Lí(h)be(h)ra(h) me(h) de(h) san(h)guí(h)ni(h)bus,(h) De(h)us,(h) De(h)us(h) sa(g)lú(ixi)tis(h) me(g)æ :(f.) \greheightstar(:) et(g) ex(g)sul(g)tá(g)bit(g) lin(g)gua(g) me(g)a(g) ju(g)stí(g)ti(g)am(d) tu(f)am.(ed..) (::)
16. Dó(h)mi(h)ne,(h) lá(h)bi(h)a(h) me(g)a(ixi) a(h)pé(g)ri(f)es :(f.) \greheightstar(:) et(g) os(g) me(g)um(g) an(g)nun(g)ti(g)á(g)bit(g) lau(g)dem(d) tu(f)am.(ed..) (::)
17. Quó(h)ni(h)am(h) si(h) vo(h)lu(h)ís(h)ses(h) sa(h)cri(h)fí(h)ci(h)um,(h) de(g)dís(ixi)sem(h) ú(g)ti(f)que :(f.) \greheightstar(:) ho(g)lo(g)cáu(g)stis(g) non(g) de(g)le(d)ctá(f)be(f)ris.(ed..) (::)
18. Sa(h)cri(h)fí(h)ci(h)um(h) De(h)o(h) spí(h)ri(h)tus(h) con(g)tri(ixi)bu(h)lá(g)tus :(f.) \greheightstar(:) cor(g) con(g)trí(g)tum(g) et(g) hu(g)mi(g)li(g)á(g)tum,(g) De(g)us,(g) non(g) de(d)spí(f)ci(f)es.(ed..) (::)
19. Be(h)ní(h)gne(h) fac,(h) Dó(h)mi(h)ne,(h) in(h) bo(h)na(h) vo(h)lun(h)tá(h)te(g) tu(ixi)a(h) Si(g)on :(f.) \greheightstar(:) ut(g) æ(g)di(g)fi(g)cén(g)tur(g) mu(g)ri(g) Je(d)rú(f)sa(f)lem.(ed..) (::)
20. Tunc(h) ac(h)cep(h)tá(h)bis(h) sa(h)cri(h)fí(h)ci(h)um(h) ju(h)stí(h)ti(h)æ,(h) o(h)bla(h)ti(h)ó(h)nes,(h) et(g) ho(ixi)lo(h)cáu(g)sta :(f.) \greheightstar(:) tunc(g) im(g)pó(g)nent(g) su(g)per(g) al(g)tá(g)re(g) tu(g)um(d) ví(f)tu(f)los.(ed..) (::)

Really Greg! I thought it was the Gregorian Association of Banal Cantors.

Can someone please tell me what GABC stands for? Pardon my ignorance but I've never seen that abbreviation.

G=Gregorian ABC=music notation system that only requires a simple text editor. Hence, GABC is a Gregorian chant music notation system that only requires a simple text editor. Of course, one has to have (available) a program that processes the "coded" text to produce the printable chant music.

Do a forum search for Gregorio. It's free and fantastic.