Clarified Add method's comments

source.go

@@ -28,7 +28,8 @@ func NewSource() *Source {
 	return &Source{CommonAttributes: newCommonAttributes()}
 }
 
-// AddAuthor adds the Person as an author to the Source. It returns an int.
+// AddAuthor adds the Person as an author to the Source. It returns its index as
+// an int.
 func (s *Source) AddAuthor(p *Person) int {
 	return addToSlice(&s.Authors, p)
 }
@@ -41,7 +42,7 @@ func (s *Source) DeleteAuthor(index int) error {
 	return nil
 }
 
-// AddCategory adds the Category to the Source. It returns an int.
+// AddCategory adds the Category to the Source. It returns its index as an int.
 func (s *Source) AddCategory(c *Category) int {
 	return addToSlice(&s.Categories, c)
 }
@@ -55,8 +56,8 @@ func (s *Source) DeleteCategory(index int) error {
 	return nil
 }
 
-// AddContributor adds the Person as a contributor to the Source. It returns an
-// int.
+// AddContributor adds the Person as a contributor to the Source. It returns its
+// index as an int.
 func (s *Source) AddContributor(c *Person) int {
 	return addToSlice(&s.Contributors, c)
 }
@@ -70,7 +71,7 @@ func (s *Source) DeleteContributor(index int) error {
 	return nil
 }
 
-// AddLink adds the Link to the Source. It returns an int.
+// AddLink adds the Link to the Source. It returns its index as an int.
 func (s *Source) AddLink(l *Link) int {
 	return addToSlice(&s.Links, l)
 }
@@ -83,7 +84,8 @@ func (s *Source) DeleteLink(index int) error {
 	return nil
 }
 
-// AddExtension adds the ExtensionElement to the Source. It returns an int.
+// AddExtension adds the ExtensionElement to the Source. It returns its index as
+// an int.
 func (s *Source) AddExtension(e *ExtensionElement) int {
 	return addToSlice(&s.Extensions, e)
 }