What It Is: an easy way to evaluate both the quality and quantity of an author's work.
How To Calculate: X, when the author has X number of papers with X or more citations.
Example: If an author has 10 articles and they have the following number of citations (50, 25, 15, 15, 6, 4, 3, 2, 2, 1), then their H-Index would be '5' as they have 5 articles that have been cited 5 or more times (their 6th most cited article was only cited 4 times).
Citation: Hirsch, J.E. (2005) An Index to Quantify an Individual's Scientific Research Output. PNAS (102), 16569-16572.
What It Is: a variation of the original H-Index that better differentiates individuals with few articles.
How To Calculate: X, when the author has X number of articles whose cumulative times cited is greater than or equal to X²
Example: Author A has 10 articles with the following number of citations (50, 20, 15, 7, 3, 3, 2, 1, 1, 0 ) and Author B has 10 articles with the following number of citations (7, 5, 5, 4, 3, 3, 2, 2, 1, 0). They have the same H-Index (4; as each has 4 articles with 4 or more citations) however Author A has a higher G-Index than Author B (Author A=10; 50+20+15+7+3+3+2+1+1+0 > 10², Author B=4; 7+5+5+4 > 4²)
Citation: Egghe, L. (2006) Theory and Practice of the new G-Index. Scientometrics (69), 131-152.
What It Is: a variation of the original H-Index that accounts for the age of the articles being cited
How To Calculate: X, when the author has X number of articles with X or more citations; however the citations are multiplied by a factor to account for age (ex. 4/y+1, where y = number of years since publication).
Example: Author A has 3 articles each has been cited 10 times, the first is 1 year old, the second is 5 years old, and the third is ten years old; if the compensating factor is 4/y+1, then the first article 'counts' for 20 citations (10 * (4/1+1)) or (10*2), the second article 'counts' for 6.6 citations (10 * (4/1+5) or (10 * 2/3), the third article 'counts' for 3.6 citations (10 * 4/1+10) or (10 * 4/11)
Citation: Sidiropoulos, A., Katsaros, D., & Manolopoulos, Y. (2006) Generalized H-Index for Disclosing Latent Facts in Citation Networks. Scientometrics (72), 253-280.