http://www.findlaptopdriver.com/specs-ipimb-ar-7h27292011/
4 x 240-pin DDR3 DIMM slots Supports Dual Channel DDR3 1333 non-ECC , un-buffered memory (Max 16GB)
since max is 16gigs, u can go either 4 x 4gigs or 2 x 8gigs...
here are some alternatives...
G.Skill Ripjaws X Series 16GB (2 x 8GB) DDR3-1333 Memory
Corsair XMS 16GB (2 x 8GB) DDR3-1333 Memory
G.Skill Ares Series 16GB (2 x 8GB) DDR3-1333 Memory
G.Skill Ripjaws Series 16GB (4 x 4GB) DDR3-1333 Memory
Corsair XMS3 16GB (4 x 4GB) DDR3-1333 Memory
G.Skill Ripjaws X Series 16GB (4 x 4GB) DDR3-1333 Memory
if u want more variants, go here...
https://pcpartpicker.com/products/memory/#s=301333&t=11&Z=16384002,16384004