Based on your knowledge about the purpose of referencing, analyse the statements below and indicate if the sources in the statements should be referenced or not, provide a suitable reason for each answer.

a$)$ A graph from a internet article

b$)$ A quotation from a handbook

c$)$ An idea of your own based on reading a journal article

d$)$ Information you found from a search in EbscoHost

e$)$ An item of common knowledge

f$)$ A theory presented in your study guide