Please provide references for the following:
Udwebo mcibisholo umqondo obhekisela izinhlobo zolimi ezikhona. Lokhu kubandakanya izinhlobo ezijwayelekile nezingajwayelekile zolimi. Umbono womdwebo mcibisholo wahlongozwa okokuqala yisazi sezilimi u-Uriel Weinreich ngeminyaka yawo-1960. U-Weinreich uveze ukuthi zonke izinhlobo zolimi zingabonwa njengezikhona ngokuqhubekayo, kungabikho uhlobo olulodwa oluyifomu "elilungile" noma "elijwayelekile". Lo mqondo kamuva wanwetshwa ezinye izazi zezilimi, ezinjengoWilliam Labov noRichard Hudson. U-Labov wenze isiphakamiso sokuthi zonke izinhlobo zolimi zisebenze ngokulinganayo, nokuthi bonke abasebenzisi bolimi babe nezinhlelo zabo zolimi ezihlukile. U-Hudson wakhela phezu kwalo mbono ngokuphakamisa ukuthi zonke izinhlobo zolimi zixhumene futhi zihlale zithonyana. Njengoba lo mqondo wahlongozwa okokuqala, uye wasetshenziselwa ukuchaza ubudlelwano phakathi kwezinhlobonhlobo zezilimi eziningi ezahlukene, okuhlanganisa isiNgisi, nesiZulu. Sekukonke, umdwebo mcibisholo ulekelela ukuqonda ukuguquguquka kolimi kanye nobudlelwano obukhona phakathi kolimi lesi Zulu nolwesiNgisi.
Weinreich, Uriel. "Languages in Contact: Findings and Problems." The Hague, Mouton, 1968.
Labov, William. "The Social Stratification of English in New York City." Washington, DC: Center for Applied Linguistics, 1966.
Hudson, Richard A. "Sociolinguistics." Cambridge University Press, 1980.