Migrating my .net wpf application from .net 4.5 to 4.0 along with sqlite? Sqlite reference is not getting resolved

I am downgrading my .net project targeted on .net4.5 to .net 4.0. I have SQlite DLLs being used in this project. when i changed target framework in project properties. biuld errors came as:

Error 11 The type or namespace name 'SQLite' does not exist in the namespace 'System.Data' (are you missing an assembly reference?) D:\Users\nehat\Desktop\skillmeterTrial\SkillMeter\SkillMeter\DataAccessLayer\DataAccessADO.cs 10 19 SkillMeter Error 12 The type or namespace name 'SQLite' does not exist in the namespace 'System.Data' (are you missing an assembly reference?) D:\Users\nehat\Desktop\skillmeterTrial\SkillMeter\SkillMeter\DataAccessLayer\SQLiteHelper.cs 10 19 SkillMeter Error 13 The type or namespace name 'SQLiteConnection' could not be found (are you missing a using directive or an assembly reference?) D:\Users\nehat\Desktop\skillmeterTrial\SkillMeter\SkillMeter\DataAccessLayer\SQLiteHelper.cs 30 24 SkillMeter

Though i have added dlls downloaded from sqlite.org. I am not able to find out the solution to thi. Can Somebody please help?