5Twitchell, David, Ed. ,Robert M. Gagne and M. David Merrill: In Conversation:Reviewing the Main Points of Robert M. Gagne's Learning Theory[J]. Educational Technology,v30 n7 ,P34- 39 ,Jul 1990.
6Twitchell, David, Ed. ,Robert M. Gagne and M. David Merrill. In Conversation.. Reviewing the Main Points of M. David Merrill's Learning Theory[J]. Educational Technology; v30 n8 P36-41 Aug 1990.
7Twitchell, David, Ed. ,Robert M. Gagne and M. David Merrill. In Conversation. No. 3.. An Overview of M. David Merrill's New Component Design Theory[J]. Educational Technology, v30 n9 P36-42 Sep 1990.
8Twitchell, David,Ed. ,Robert M. Gagne and M. David Merrill, In Conversation: A Look at the Differences between the Theories of Robert M. Gagne and M. David Merrill[J]. Educational Technology; v30 nl0 p37-45 Oct 1990.
9Twitchell, David ,Ed. , Robert M. Gagne and M. David Merrill, In Conversation : A Comparison of Robert M. Gagne's. Events of Instruction and M. David Merrill's Component Display Theory[J]. Educational Technology ; v30 n11 p35-39 Nov 1990.
10Twitchell, David ,Ed. ,Robert M. Gagne and M. David Merrill: In Conversation:The Cognitive Psychological Basis for Instructional Design[J]. Educational Technology t v30 n12 p35-46 Dec 1990.
