[1] Bary, N. K.: 
A treatise on trigonometric series. Pergamon Press, Oxford–London–New York–Paris–Frankfurt, 1964. 
Zbl 0129.28002[2] Fomin, G. A.: 
On linear methods for summing Fourier series. Math. Sbornik 66 (1964), 144–152. 
MR 0168988[3] Garret, W. J., Stanojević, Č. V.: On integrability and $L^1$–convergence of certain cosine sums. Notices, Amer. Math. Soc. 22 (1975), A–166.
[4] Garret, W. J., Stanojević, Č. V.: 
On $L^1$–convergence of certain cosine sums. Proc. Amer. Math. Soc. 54 (1976), 101–105. 
MR 0394002[5] Hooda, N., Ram, B., Bhatia, S. S.: 
On $L^1$–convergence of a modified cosine sum. Soochow J. of Math. 28 (3) (2002), 305–310. 
MR 1926327 | 
Zbl 1019.42002[6] Kaur, J., Bhatia, S. S.: 
Integrability and $L^{1}$–convergence of certain cosine sums. Kyungpook Math. J. 47 (2007), 323–328. 
MR 2413939 | 
Zbl 1143.42300[8] Kaur, J., Bhatia, S. S.: 
 A class of $L^1$–convergence of new modified cosine sums. Southeast Asian Bull. Math. 36 (2012), 831–836. 
MR 3057813[9] Kaur, K.: On $L^1$–convergence of a modified sine sums. Electronic J. Geogr. Math. 14 (1) (2003).
[10] Kaur, K.: 
Integrability and $L sp 1$–convergence of Rees–Stanojevic sums with generalized semi–convex coefficients of non–integral orders. Arch. Math. (Brno) 41 (4) (2005), 423–437. 
MR 2195495[12] Kaur, K., Bhatia, S. S., Ram, B.: 
Integrability and $L^{1}$–convergence of modified sine sums. Georgian Math. J. 11 (1) (2004), 99–104. 
MR 2065543 | 
Zbl 1051.42004[13] Krasniqi, Xh. Z.: 
A note on $L^1$–convergence of the sine and cosine trigonometric series with semi–convex coefficients. Int. J. Open Probl. Comput. Sci. Math. 2 (2) (2009), 231–239. 
MR 2524696 | 
Zbl 1208.42002[15] Kumari, S., Ram, B.: 
$L^{1}$–convergence of certain trigonometric sums. Indian J. Pure Appl. Math. 20 (9) (1989), 908–914. 
MR 1015638[16] Leindler, L.: 
Additions to the Telyakovskiĭ class $S$. J. Inequal. Pure Appl. Math. 4 (2) (2003), 5, electronic only. 
MR 1994248[17] Ram, B.: 
Convergence of certain cosine sums in the metric space $L$. Proc. Amer. Math. Soc. 66 (1977), 258–260. 
MR 0461013 | 
Zbl 0367.42011[18] Sidon, S.: 
Hinreichende Bedingungen für den Fourier-Charakter einer trigonometrischen Reihe. J. London Math. Soc. 14 (1939), 1528–160. 
Zbl 0021.40301[19] Singh, K., Kaur, K.: 
On $L^{1}$–convergence of certain generalized modified trigonometric sums. Mat. Vesnik 61 (3) (2009), 219–226. 
MR 2546612 | 
Zbl 1265.42012[20] Singh, N., Sharma, K. M.: 
Convergence of certain cosine sums in the metric space $L$. Proc. Amer. Math. Soc. 75 (1978), 117–120. 
MR 0503543[21] Telyakovskiĭ, S. A.: 
On a sufficient condition of Sidon for integrability of trigonometric series. Math. Zametki 14 (1973), 317–328. 
MR 0328456[22] Tomovski, Ž.: 
Some results on $L^1$–approximation of the $r$–th derivative of Fourier series. J. Inequal. Pure Appl. Math. 1 (2002), 11, electronic only. 
Zbl 0999.42004