• HTN planning
• Reduction schemas
• HTN algorithm
• Critics
• NONLIN
• Plan networks
• Use-when (filter) conditions
• TOME, GOST
• Adding backtracking to NOAH
• SIPE
• Representation
• Critics

Yang, Q. "Formalizing Planning Knowledge for Hierarchical Planning." Computational Intelligence Journal, 6(2), (1990). NOTE: ONLY SECTIONS 1 & 2.

• Description of action reduction schemas and HTN planning algorithm

Tate, A. "Generating Project Networks". In Allen, J, Hendler, J., and Tate, A. "Readings in Planning", Morgan Kaufmann, 1990.

• Good description of NONLIN

Wilkins, D. E. "Domain-Independent Planning: Representation and Plan Generation" Artificial Intelligence, Vol 22, pp. 269-301, 1984.

• Good overview of the initial version of SIPE