Where did Breivik learn his bomb making skills to be able to create a bomb from fertilizer in his farmhouse that was big enough to be able to destroy his Government building?
We are led to believe Breivik is a "solo terrorist" connected to no one who had no physical or mental help in any capacity within the totality of his actions because to state that he did would mean there is a bigger story surrounding him and other people's involvement and it is this that the Norwegian's in control of the case do not want the public to know.
There is no possible way that Breivik made a bomb from fertilizer that was big enough to blow up his Government building without prior training and test detonating of his creation.
As you can see from the picture Breivik did not test detonate any bombs at his farm house due to the fact of how close his neighbours lived.
So what is the explanation behind the bomb?
It is another line of investigation completely dismissed from the public mind because it conflicts with the 'official' story surrounding Breivik of the "solo terrorist" connected to no one.
Further reading: A question of doubt