Update entityRelationshipDiagram.md

packages/mermaid/src/docs/syntax/entityRelationshipDiagram.md

@@ -1,6 +1,6 @@
 # Entity Relationship Diagrams
 
-> An entity–relationship model (or ER model) describes interrelated things of interest in a specific domain of knowledge. A basic ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between entities (instances of those entity types). Wikipedia.
+> An entity–relationship model (or ER model) describes interrelated things of interest in a specific domain of knowledge. A basic ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between entities (instances of those entity types) [Wikipedia](https://en.wikipedia.org/wiki/Entity%E2%80%93relationship_model).
 
 Note that practitioners of ER modelling almost always refer to _entity types_ simply as _entities_. For example the `CUSTOMER` entity _type_ would be referred to simply as the `CUSTOMER` entity. This is so common it would be inadvisable to do anything else, but technically an entity is an abstract _instance_ of an entity type, and this is what an ER diagram shows - abstract instances, and the relationships between them. This is why entities are always named using singular nouns.
 
@@ -75,7 +75,7 @@ Only the `first-entity` part of a statement is mandatory. This makes it possible
 
 The `relationship` part of each statement can be broken down into three sub-components:
 
-- the cardinality of the first entity with respect to the second,
+- the cardinality of the first entity with respect to the second
 - whether the relationship confers identity on a 'child' entity
 - the cardinality of the second entity with respect to the first
 
@@ -162,7 +162,7 @@ erDiagram
 
 #### Attribute Keys and Comments
 
-Attributes may also have a `key` or comment defined. Keys can be `PK`, `FK` or `UK`, for Primary Key, Foreign Key or Unique Key. To specify multiple key constraints on a single attribute, separate them with a comma (e.g., `PK, FK`).. A `comment` is defined by double quotes at the end of an attribute. Comments themselves cannot have double-quote characters in them.
+Attributes may also have a `key` or comment defined. Keys can be `PK`, `FK` or `UK`, for Primary Key, Foreign Key or Unique Key. To specify multiple key constraints on a single attribute, separate them with a comma (e.g., `PK, FK`). A `comment` is defined by double quotes at the end of an attribute. Comments themselves cannot have double-quote characters in them.
 
 ```mermaid-example
 erDiagram