I request the assistance I work on the library database, But I have problem on the erd and relationship between entity ,if any one can help me I am grateful to him .
this my project if any one can add some entity and the erd please:
The system contains entities that act and participate with the system , these entities are :

Employee Entity : each employee has an ID, Name, DOB , Address , telephone # , and supervised by other employee. The employee deal with supplier who supply the books, and treat each order comes from customer

Book Entity : each book has an ID , Name , Author Name , Book Category , and Price of the book.

Customer Entity : each customer has an ID, Name, Address , Telephone # , the customer is person who borrowing books from the library .

Supplier Entity : each supplier has an ID , Name , Telephone # , Address , the supplier is supply the library with different category of books.

Order Entity : each order has an ID , order date , delivery date , ID for the employee , and the ID for the customer who borrowed the books , Quantity of the order .

well the first apparent error i see is the many to many relationship between the book and customer as one book can be loaned by many customer and a customer can loan many books, it is also not uncommon for a library to more than one copy of the same book, instead you should have a composite entity between customer and book entities and have a book_loan entity. also i hope you're not using the book's ISBN number as the primary that could be troublesome if you have more than one copy a book instead use a composite primary key (the ISBN and a surrogate key).

thank you for suggestion
please if you can see the diagram and modify it

im put it in attach file .

thank you for suggestion
im want to sent erd for to modify it if you can

thank you too much

yes im see
once more

ouch you use chen model i'll have a look at it and try and make out heads or tails from that doc

thank you very much