@ARTICLE{sample1,
 AUTHOR         = "Author",
 TITLE          = {Article title},
 JOURNAL        = "Journal",
 VOLUME		= Volume,
 PAGES		= "numbers",
 YEAR           = year
}

@BOOK{sample2,
 AUTHOR         = "Author",
 TITLE          = {title},
 EDITION	= edition,
 ADDRESS	= "place of publication",
 PUBLISHER	= publisher,
 YEAR		= year
}

@BOOK{sample3,
 AUTHOR         = "Author", 
 TITLE          = {title},        
 EDITION        = edition,
 ADDRESS        = "place of publication",
 PUBLISHER      = publisher,
 YEAR           = year
}

@ARTICLE{sample4,
 AUTHOR         = "Author",
 TITLE          = {Article title},
 JOURNAL        = "Journal",
 VOLUME         = Volume,
 PAGES          = "numbers",     
 YEAR           = year
}