@article{Schwikowski2002, 
     author = "Schwikowski, Benno and Speckenmeyer, Ewald", 
     doi = "10.1016/S0166-218X(00)00339-5", 
     issn = "0166218X", 
     journal = "Discrete Applied Mathematics", 
     keyword = "enumeration algorithm,feedback arc sets,feedback vertex sets,polynomial delay", 
     link = "http://linkinghub.elsevier.com/retrieve/pii/S0166218X00003395", 
     month = "mar", 
     number = "1-3", 
     pages = "253--265", 
     title = "On enumerating all minimal solutions of feedback problems", 
     uri = "http://linkinghub.elsevier.com/retrieve/pii/S0166218X00003395", 
     volume = "117", 
     year = "2002", 
}

Problems: 22 23 24