Jay Conrad Levinson (2007). “Guerrilla Marketing, 4th edition: Easy and Inexpensive Strategies for Making Big Profits from Your SmallBusiness”, p.3, Houghton Mifflin Harcourt
Jay Conrad Levinson (2007). “Guerrilla Marketing, 4th edition: Easy and Inexpensive Strategies for Making Big Profits from Your SmallBusiness”, p.8, Houghton Mifflin Harcourt