We define Casson–Gordon –invariants for links and give a lower bound of the slice genus of a link in terms of these invariants. We study as an example a family of two component links of genus and show that their slice genus is , whereas the Murasugi–Tristram inequality does not obstruct this link from bounding an annulus in the 4–ball.
"On the slice genus of links." Algebr. Geom. Topol. 3 (2) 905 - 920, 2003. https://doi.org/10.2140/agt.2003.3.905