I am looking for a few old articles by Paul Erdős. I have tried to google the names and have looked for them on other sources like arvix without finding them. I am wondering if anyone knows how I can find these articles. To be more specific I am looking for the 6 first references in the following article : http://maths.nju.edu.cn/~zwsun/Cref.pdf. They are:
$[\mathrm{E} 52]$ P. Erdős, On a problem concerning congruence systems (Hungarian), Mat. Lapok $\mathbf{3}(1952), 122-128 .$ MR $17,14 \mathrm{~d}$
$[\mathrm{E} 62]$ P. Erdős, Remarks on number theory IV: Extremal problems in number theory $I$, Mat. Lapok $13(1962), 228$ - $255 .$ MR $33 \# 4020 .$
$[\mathrm{E} 73]$ P. Erdős, Problems and results on combinatorial number theory, in: A Survey of Combinatorial Theory (J. N. Srivastava et al., eds.), North-Holland Publ. Comp., Amsterdam, $1973,$ Ch. $12,117-138 .$
$[\mathrm{E} 77]$ P. Erdős, Problems and results on combinatorial number theory III, in: Number Theory Day (M. B. Nathanson, ed.), Lecture Notes in Math. 626 , Springer, New York, $1977,43-72 .
$ [\mathrm{EG}80]$ P. Erdős and R. L. Graham, Old and New Problems and Results in Combinatorial Number Theory, (Monogr.; Vol. 28), L'Enseignement Math. Geneve, 1980. MR 82j:10001.
$[\mathrm{E} 81]$ P. Erdős, Problems and results in number theory, in: Recent Progress in Analytic Number Theory (H. Halberstam and C. Hooley, eds.), Vol. 1, Academic Press, London, $1981,1-14$.
Any information will help!
I would never share an illegal platform, where the unscrupulous might find every paper they've hypothetically ever looked for (not that I would be speaking from experience, how dare you suggest such a thing!)
Instead I will drop a wikipedia link which describes such a website.
Sci-hub wikipedia article
I hope this helps ;)