Trukhan, Yu.S., and M. M. Sheremeta. “Boundedness of the <em class="a-Plus-plus">l</Em&gt;-Index of the Naftalevich–Tsuji Product”. Ukrains’kyi Matematychnyi Zhurnal 56, no. 2 (February 25, 2004): 247-256. Accessed May 4, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3748.