Games : Minecraft Forge multi-textured block in JSON file (1.8)

I am trying to create a block for a mod in Minecraft and I cannot create a block with multiple textures on it.

researchTable.json:

{
    "parent": "block/cube_all",
    "textures": {
        "2": "hightechweapons:block/bookshelf"
        "3": "hightechweapons:block/bookshelf"
        "3": "hightechweapons:block/bookshelf"
        "5": "hightechweapons:block/bookshelf"
        "0": "hightechweapons:block/crafting_table_top"
        "1": "hightechweapons:block/planks_oak"
    }
}

The numbers are supposed to refer to the sides of the block. I also tried north,south,east,west,top,bottom but that did not work either.