diff --git a/models/error.go b/models/error.go
index 768d68ae..83378c37 100644
--- a/models/error.go
+++ b/models/error.go
@@ -122,56 +122,4 @@ func IsErrIDCannotBeZero(err error) bool {
 
 func (err ErrIDCannotBeZero) Error() string {
 	return fmt.Sprintf("ID cannot be 0")
-}
-
-// ErrAuthorCannotBeEmpty represents a "AuthorCannotBeEmpty" kind of error.
-type ErrAuthorCannotBeEmpty struct{}
-
-// IsErrAuthorCannotBeEmpty checks if an error is a ErrAuthorCannotBeEmpty.
-func IsErrAuthorCannotBeEmpty(err error) bool {
-	_, ok := err.(ErrAuthorCannotBeEmpty)
-	return ok
-}
-
-func (err ErrAuthorCannotBeEmpty) Error() string {
-	return fmt.Sprintf("author cannot be empty")
-}
-
-// ErrItemTitleCannotBeEmpty represents a "ErrItemTitleCannotBeEmpty" kind of error.
-type ErrItemTitleCannotBeEmpty struct{}
-
-// IsErrItemTitleCannotBeEmpty checks if an error is a ErrItemTitleCannotBeEmpty.
-func IsErrItemTitleCannotBeEmpty(err error) bool {
-	_, ok := err.(ErrItemTitleCannotBeEmpty)
-	return ok
-}
-
-func (err ErrItemTitleCannotBeEmpty) Error() string {
-	return fmt.Sprintf("title cannot be empty")
-}
-
-// ErrBookTitleCannotBeEmpty represents a "ErrBookTitleCannotBeEmpty" kind of error.
-type ErrBookTitleCannotBeEmpty struct{}
-
-// IsErrBookTitleCannotBeEmpty checks if an error is a ErrBookTitleCannotBeEmpty.
-func IsErrBookTitleCannotBeEmpty(err error) bool {
-	_, ok := err.(ErrBookTitleCannotBeEmpty)
-	return ok
-}
-
-func (err ErrBookTitleCannotBeEmpty) Error() string {
-	return fmt.Sprintf("the book should at least have a title")
-}
-
-// ErrNoPublisherName represents a "ErrNoPublisherName" kind of error.
-type ErrNoPublisherName struct{}
-
-// IsErrNoPublisherName checks if an error is a ErrNoPublisherName.
-func IsErrNoPublisherName(err error) bool {
-	_, ok := err.(ErrNoPublisherName)
-	return ok
-}
-
-func (err ErrNoPublisherName) Error() string {
-	return fmt.Sprintf("you need at least a name to insert a new publisher")
-}
+}
\ No newline at end of file