diff --git a/README.md b/README.md
index c6b751d..015faa3 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,19 @@ to organize the files of the project according to what they do. This means that
 templates are grouped together in one directory, static in another and views in
 a third (copy/paste from Flask documentation).
 
+### DB relationships:
+
+ **Author -> Book** should be a many-to-many relationship as multiple authors can
+share the ownership of a book.
+
+For example, authors A and B wrote the book X. When listing all the books
+written by author A, book X must appear in the results. Likewise when
+listing the books written by author B.
+
+If we want to use a one-to-one relationship, the book X should only be
+returned as part of the results if we search by "the books written by author
+A **and** author B" working together.
+
 ## Usage
 ```
 flask --app app --debug run
diff --git a/app/models.py b/app/models.py
index 52925a6..a45da92 100644
--- a/app/models.py
+++ b/app/models.py
@@ -17,3 +17,24 @@ class Book(db.Model):
     shared = db.Column(db.Boolean, default=False)
     rating = db.Column(db.Integer)
     id_user = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
+    id_author = db.Column(db.Integer, db.ForeignKey('author.id'), nullable=False)
+    id_editorial = db.Column(db.Integer, db.ForeignKey('editorial.id'), nullable=False)
+
+class Author(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(255), nullable=False)
+    country = db.Column(db.String(255))
+
+class Editorial(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(255), nullable=False)
+
+# many-to-many books/tags
+tags = db.Table('books_tags',
+                db.Column('id_tag', db.Integer, db.ForeignKey('tag.id'), primary_key=True),
+                db.Column('id_book', db.Integer, db.ForeignKey('book.id'), primary_key=True)
+        )
+
+class Tag(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(255), primary_key=True)
diff --git a/migrations/versions/11ddd75a4034_.py b/migrations/versions/11ddd75a4034_.py
new file mode 100644
index 0000000..232897f
--- /dev/null
+++ b/migrations/versions/11ddd75a4034_.py
@@ -0,0 +1,36 @@
+"""empty message
+
+Revision ID: 11ddd75a4034
+Revises: a56eb0f88d08
+Create Date: 2022-08-07 22:47:25.294115
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '11ddd75a4034'
+down_revision = 'a56eb0f88d08'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('editorial',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('name', sa.String(length=255), nullable=False),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.add_column('book', sa.Column('id_editorial', sa.Integer(), nullable=False))
+    op.create_foreign_key(None, 'book', 'editorial', ['id_editorial'], ['id'])
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_constraint(None, 'book', type_='foreignkey')
+    op.drop_column('book', 'id_editorial')
+    op.drop_table('editorial')
+    # ### end Alembic commands ###
diff --git a/migrations/versions/2f3143ca16e9_.py b/migrations/versions/2f3143ca16e9_.py
new file mode 100644
index 0000000..cc44ddc
--- /dev/null
+++ b/migrations/versions/2f3143ca16e9_.py
@@ -0,0 +1,33 @@
+"""empty message
+
+Revision ID: 2f3143ca16e9
+Revises: 70f7fdfafc25
+Create Date: 2022-08-07 18:04:12.614018
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '2f3143ca16e9'
+down_revision = '70f7fdfafc25'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('author',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('name', sa.String(length=255), nullable=False),
+    sa.Column('country', sa.String(length=255), nullable=True),
+    sa.PrimaryKeyConstraint('id')
+    )
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_table('author')
+    # ### end Alembic commands ###
diff --git a/migrations/versions/5c34faeea863_.py b/migrations/versions/5c34faeea863_.py
new file mode 100644
index 0000000..64b6a0e
--- /dev/null
+++ b/migrations/versions/5c34faeea863_.py
@@ -0,0 +1,39 @@
+"""empty message
+
+Revision ID: 5c34faeea863
+Revises: 11ddd75a4034
+Create Date: 2022-08-07 23:25:27.237821
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '5c34faeea863'
+down_revision = '11ddd75a4034'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('tag',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.create_table('tags',
+    sa.Column('id_tag', sa.Integer(), nullable=False),
+    sa.Column('id_book', sa.Integer(), nullable=False),
+    sa.ForeignKeyConstraint(['id_book'], ['book.id'], ),
+    sa.ForeignKeyConstraint(['id_tag'], ['tag.id'], ),
+    sa.PrimaryKeyConstraint('id_tag', 'id_book')
+    )
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_table('tags')
+    op.drop_table('tag')
+    # ### end Alembic commands ###
diff --git a/migrations/versions/68152efb549c_.py b/migrations/versions/68152efb549c_.py
new file mode 100644
index 0000000..bfda19b
--- /dev/null
+++ b/migrations/versions/68152efb549c_.py
@@ -0,0 +1,44 @@
+"""empty message
+
+Revision ID: 68152efb549c
+Revises: 5c34faeea863
+Create Date: 2022-08-07 23:26:05.032691
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import mysql
+
+# revision identifiers, used by Alembic.
+revision = '68152efb549c'
+down_revision = '5c34faeea863'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('books_tags',
+    sa.Column('id_tag', sa.Integer(), nullable=False),
+    sa.Column('id_book', sa.Integer(), nullable=False),
+    sa.ForeignKeyConstraint(['id_book'], ['book.id'], ),
+    sa.ForeignKeyConstraint(['id_tag'], ['tag.id'], ),
+    sa.PrimaryKeyConstraint('id_tag', 'id_book')
+    )
+    op.drop_table('tags')
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('tags',
+    sa.Column('id_tag', mysql.INTEGER(display_width=11), autoincrement=False, nullable=False),
+    sa.Column('id_book', mysql.INTEGER(display_width=11), autoincrement=False, nullable=False),
+    sa.ForeignKeyConstraint(['id_book'], ['book.id'], name='tags_ibfk_1'),
+    sa.ForeignKeyConstraint(['id_tag'], ['tag.id'], name='tags_ibfk_2'),
+    sa.PrimaryKeyConstraint('id_tag', 'id_book'),
+    mysql_default_charset='latin1',
+    mysql_engine='InnoDB'
+    )
+    op.drop_table('books_tags')
+    # ### end Alembic commands ###
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diff --git a/migrations/versions/__pycache__/b9d22c840958_.cpython-39.pyc b/migrations/versions/__pycache__/b9d22c840958_.cpython-39.pyc
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diff --git a/migrations/versions/a56eb0f88d08_.py b/migrations/versions/a56eb0f88d08_.py
new file mode 100644
index 0000000..bf98032
--- /dev/null
+++ b/migrations/versions/a56eb0f88d08_.py
@@ -0,0 +1,28 @@
+"""empty message
+
+Revision ID: a56eb0f88d08
+Revises: ab8d661b4728
+Create Date: 2022-08-07 22:43:43.906499
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'a56eb0f88d08'
+down_revision = 'ab8d661b4728'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('author', sa.Column('name', sa.String(length=255), nullable=False))
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('author', 'name')
+    # ### end Alembic commands ###
diff --git a/migrations/versions/ab8d661b4728_.py b/migrations/versions/ab8d661b4728_.py
new file mode 100644
index 0000000..c25f77c
--- /dev/null
+++ b/migrations/versions/ab8d661b4728_.py
@@ -0,0 +1,32 @@
+"""empty message
+
+Revision ID: ab8d661b4728
+Revises: 2f3143ca16e9
+Create Date: 2022-08-07 18:07:37.773083
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import mysql
+
+# revision identifiers, used by Alembic.
+revision = 'ab8d661b4728'
+down_revision = '2f3143ca16e9'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('author', 'name')
+    op.add_column('book', sa.Column('id_author', sa.Integer(), nullable=False))
+    op.create_foreign_key(None, 'book', 'author', ['id_author'], ['id'])
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_constraint(None, 'book', type_='foreignkey')
+    op.drop_column('book', 'id_author')
+    op.add_column('author', sa.Column('name', mysql.VARCHAR(length=255), nullable=False))
+    # ### end Alembic commands ###
diff --git a/migrations/versions/b9d22c840958_.py b/migrations/versions/b9d22c840958_.py
new file mode 100644
index 0000000..44954d1
--- /dev/null
+++ b/migrations/versions/b9d22c840958_.py
@@ -0,0 +1,28 @@
+"""empty message
+
+Revision ID: b9d22c840958
+Revises: 68152efb549c
+Create Date: 2022-08-07 23:27:11.651513
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'b9d22c840958'
+down_revision = '68152efb549c'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('tag', sa.Column('name', sa.String(length=255), nullable=False))
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('tag', 'name')
+    # ### end Alembic commands ###