  In this paper, we show that all the bilinear Adler-Bobenko-Suris (ABS)
equations (except Q2 and Q4) can be obtained from symmetric discrete AKP system
by taking proper reductions and continuum limits. Among the bilinear ABS
equations, a simpler bilinear form of the ABS H2 equation is given. In
addition, an 8-point 3-dimensional lattice equation and an 8-point
4-dimensional lattice equation are obtained as by-products. Both of them can be
considered as extensions of the symmetric discrete AKP equation.
