Citation linking 
For: builds on established journal authoring procedures, already a prominent feature of advanced online journals 
Against: needs to be comprehensive, large data sources required 

Keyword linking  
For: works in small-scale, well-defined cases with careful editorial control 
Against: can produce too many links, difficult to control, difficult to describe or label link destinations, difficult to manage user expectations, authors wary of links superimposed on text 

PDF linking 
For: Web linking mechanisms are well established for HTML, but most online journals are in PDF, so this could be important for publishers of PDF journals 
Against: difficult to maintain, dependent on support for proprietary software - may be version dependent, complex and expensive in terms of computing resources