1.  Sybil Noyes, Charles Thornton Libby, & Walter Goodwin Davis.  1928-39.  Genealogical Dictionary of Maine and New Hampshire.  Southworth- Anthoensen Press, Portland, ME (republ. 1972ff by Genealogical Publ. Co., Baltimore, MD; Broderbund CD-523).  On p. 633 (bold-face as per original):

SIAS, very uncommon. 1 ____, mar. a dau. of William Roberts(14), who mar. 2d Salathiel Denbo(1) and 3d William Graves(6). Son John appears. See also (2). One John Size, residence unkn., was a soldier under Capt. Moseley in 1675.

2.  Walter Goodwin Davis.  1996.  Massachusetts and Maine Families in the Ancestry of Walter Goodwin Davis (1885-1996):  a Reprinting, in Alphabetical Order by Surname, of the Sixteen Multi-Ancestor Compendia (plus Thomas Haley of Winter Harbor and His Descendants) compiled by Maine's Foremost Genealogist, 1916-1963. Genealogical Publ. Co., Baltimore, MD (Broderbund CD-194).  In Vol. III, pp. 229-233, is a section entitled, "Roberts, of Oyster River, New Hampshire (from Lydia Harmon, 1924)."  This section appears to be a verbatim excerpt from The Ancestry of Lydia Harmon.  I cannot quote the section in its entirely because of copyright contraints, but here are the paragraphs most relevant to SIAS:

p. 229	...the Roberts farm was sold to William and Ezekiel Pitman on January 23, 1664...
p. 230	William Roberts and one of his sons-in-law were killed by Indians in 1675, during King Philip's War... From the account [of his estate] ... it appears that Roberts was survived by his wife and that his son, William Roberts, died before 1677...    The name of William Robert's wife is not known.     The number and names of William Robert's children are determined by the deeds disposing of the two hundred-acre town grants.  The property was conveyed in "one-fifth parts" by Elizabeth Allen, Sarah Harmon, Grace Moses and Hannah Cox, all stating that they were daughters of William Roberts.  This leaves only one fifth to be accounted for, and proves that at the date of the division no son of William Roberts was living to inherit a double portion.  The last fifth was held in shares, of which two were conveyed by John Sias and Ann, his wife, and one by Richard Denbow, on the same day, to Salathiel Denbow, who later conveyed all his rights in the property of his grandfather, William Roberts.  From these facts the theory is advanced that a daughter of William Roberts married, first, a Sias -- the son-in-law who was killed by the Indians with her father in 1675 -- by whom she had a son, John Sias, who inherited an eldest son's
p. 231	double portion of her estate and that she married, second, Salathiel Denbow, senior, and by him had several other children.    Children [of William ROBERTS]...   ii.  A DAUGHTER.  As stated above, there is evidence pointing to the conclusion that she m. _____ Sias, and, after his death in 1675, m. Salathiel Denbow.  Denbow was born in 1642, according to his own statement in a deposition.  He was in Oyster River in 1666, and d. before 1714.  The name was often spelled Denmore and is now Dinsmore.  His wife survied him and married William Graves as her last husband, he being named as their "father-in-law" by her children in their deeds of their Roberts inheritance.    Child, by first husband [Mr. SIAS]:--    1.  John Sias.  He m. Anne Pitman in Wells in 1698.  She was b. about 1672, and was undoubtedly the daughter Anne mentioned in the will of William Pitman of Oyster River in 1682.  They conveyed their two shares of land which formerly belonged to William Roberts to Salathiel Denbow in 1724.    Children, by second husband [Mr. DENBOW]:--...

The remainder of the section gives the children of Mr. & Mrs. (SIAS) DENBOW, then the remaining children of William ROBERTS.