Lithium abundances versus age. The Li abundance of HIP 68468 was determined in this work. For the field solar twins (circles, triangles, squares) we used the values given in our previous works (Carlos et al. 2016; Galarza et al. 2016a; Meléndez et al. 2012, 2014a,b; Monroe et al. 2013; Ramírez et al. 2011), and for the solar twins in open clusters (pentagons) we adopted the values given in Baumann et al. (2010) and Castro et al. (2011), as described in the text. We also show non-standard models of lithium depletion (Charbonnel & Talon 2005; do Nascimento et al. 2009; Xiong & Deng 2009; Denissenkov 2010), normalised to the Sun.