The appearance of the 1,500-page document, which Breivik placed online before embarking on Friday's devastating attack, includes parts written by the suspect which were taken almost word for word from the writings of the American "Unabomber" Ted Kaczynski.
The passages copied by Breivik appear in the first few pages of Kaczynski's manifesto. Breivik changed a Kaczynski screed on leftism and what he considered to be leftists' "feelings of inferiority" - mainly by substituting the words "multiculturalism" or "cultural Marxism" for "leftism".
According to the Daily Telegraph, Breivik identified a British mentor called Richard in his polemic. He claimed that he was recruited by two English right-wing extremists at a meeting in the UK in 2002, which seven other people attended.
The writings also provide a detailed - and terrifying - portrait of a meticulous and calculated planner who contrived to ensure maximum casualties and that he wouldn't be caught.
Entitled "2083 - A European Declaration of Independence", the manifesto reveals how the six-foot bodybuilder spent eight years planning his attacks.
Breivik is reported to hold extreme Christian fundamentalist views and is understood to have criticised multi-culturalism and Muslim immigration in his manifesto.
The image that has begun to emerge is of a man with a disconnected and shadowy past.
A loner who had few friends, he seemed to spend much of his spare time frequenting internet forums for far-right activists, neo-Nazis and Christian fundamentalists.
A former member of Norway's anti-immigrant Progress Party, Breivik apparently loved violent video games like the best-selling Modern Warfare and said his favourite TV show was Dexter, the popular HBO drama about a serial killer who murders evil people.
Unlike many mass murderers, who kill themselves rather than be taken, Breivik surrendered to police. And unlike the victims of the past killers, his were not randomly slaughtered, or in the wrong place at the wrong time. Each was targeted for their links to Norway's Labour Party.
Caroline Slatti (22) a neighbour who lives in the same block of flats on Hoffsveien, remembered a quiet but unremarkable man with a sociable mother who tended to his every need.
"He looked like an ordinary guy, he was just like anybody else," she said. "I didn't know him all that well but his mother is really friendly. She dotes on him and always talks about him."
As police investigated the suspect's background, details emerged of his possible affiliations with extremists in the UK.
The right-wing English Defence League, with whom he was said to have been involved, denied that Breivik (32) had any links with them and said they "vehemently" opposed his actions.
In a statement on its website the group wrote: "Terrorism and extremism of any kind is never acceptable and we pride ourselves on opposing these."
The Nordic Defence League also distanced itself from the killings, posting a message on its Facebook page saying: "We condemn this act of terror no matter who or where this came from!"