I use the following conventions in the references :

• PDA = Programming: The Derivation of Algorithms

Programming Exercises, via Kaldewaij

• The number of array element pairs whose product is positive
• All array elements positive?
• The maximum element
• The maximum pair difference
• The maximum squared difference
• The maximum non-empty segment sum
• The existence of the true-false pivot
• Maximal credit
• The maximum segment product
• Multiplication
• The exponent of 3 in the prime factorisation of N
• Base X to decimal conversion
• fusc
• At least one zero element
• The existence of a particular subsequence