Topic	2001–2012	2013–present
problem involving linear second order, homogeneous equations	[7]	[Mass spring system(4)] [1] [3] [5] [4] [6] [3a] [3b] [4a] [4b] [4c] [6] [1] [4a] [6] [1] [3] [5a] [5b] [7a] [7b] [7d]
problem involving the theory of second (or higher) order linear equations		[5a] [Linearity redux(2)] [3] [5] [6] [3] [3] [3] [4] [4] [7a] [3a] [3b] [5] [5c] [7] [3]
problem involving modeling with 2nd (or higher) order linear equations without forcing (e.g., spring problems without forcing)	[Mass spring system(4a)] [Mass spring system(4b)]	[Mass spring system(4)] [More Lasers(7)] [4] [4] [4] [4] [6a] [2]
problem involving modeling with 2nd (or higher) order linear equations (e.g., spring problems with forcing)	[7]	[Chemical Reaction(3)] [RLC Circuit(4)] [Laser Model(7)] [5c] [6] [3b] [Another ruby laser(4)] [Another ruby laser(4c)] [6b] [More Lasers(7c)] [5] [4b] [4c] [3] [1a] [1b]
problem involving the use of the method of undetermined coefficients		[1a] [1] [1] [1a] [1b] [1b] [3a] [5a] [4] [6] [1] [7b] [1] [3] [1] [4]
problem involving the use of variation of parameters		[1b] [6a] [Another ruby laser(4b)] [3c] [3d] [5]
problem involving drawing or using a phase plane, including to analyze a nonlinear system		[4] [4] [6] [7] [7]
a problem consisting of true/false parts	[5]	[5] [5] [8]
problem involving the definition of the Laplace transform		[3b] [6b] [2] [1a] [2c] [4a] [3]
problem involving the linearity or other properties of the Laplace transform		[5b] [5b] [5d] [5e] [6] [7c] [2] [3a] [1b] [2] [5] [4b] [6] [7]
problem using laplace transforms to solve a differential equation		[2a] [2b] [2a] [2b] [3a] [5b] [6c] [7] [1] [3b] [2a] [2b] [7] [2] [5] [7c] [2] [4c] [6b] [6c] [7c] [6] [7]
problem using laplace transforms to solve a differential equation with discontinuous (step function) or impulse (delta function) forcing		[5c] [6b] [2c]